Malpighian tubules are critical organs for epithelial fluid transport and stress tolerance in ins... more Malpighian tubules are critical organs for epithelial fluid transport and stress tolerance in insects, and are under neuroendocrine control by multiple neuropeptides secreted by identified neurons. Here, we demonstrate roles for CRF-like diuretic hormone 44 (DH44) and Drosophila melanogaster kinin (Drome-kinin, DK) in desiccation and starvation tolerance. Gene expression and labelled DH44 ligand binding data, as well as highly selective knockdowns and/or neuronal ablations of DH44 in neurons of the pars intercerebralis and DH44 receptor (DH44-R2) in Malpighian tubule principal cells, indicate that suppression of DH44 signalling improves desiccation tolerance of the intact fly. Drome-kinin receptor, encoded by the leucokinin receptor gene, LKR, is expressed in DH44 neurons as well as in stellate cells of the Malpighian tubules. LKR knockdown in DH44-expressing neurons reduces Malpighian tubule-specific LKR, suggesting interactions between DH44 and LK signalling pathways. Finally, alt...
Malpighian tubules are critical organs for epithelial fluid transport and stress tolerance in ins... more Malpighian tubules are critical organs for epithelial fluid transport and stress tolerance in insects, and are under neuroendocrine control by multiple neuropeptides secreted by identified neurons. Here, we demonstrate roles for CRF-like diuretic hormone 44 (DH 44) and Drosophila melanogaster kinin (Drome-kinin, DK) in desiccation and starvation tolerance. Gene expression and labelled DH 44 ligand binding data, as well as highly selective knockdowns and/or neuronal ablations of DH 44 in neurons of the pars intercerebralis and DH 44 receptor (DH 44-R2) in Malpighian tubule principal cells, indicate that suppression of DH 44 signalling improves desiccation tolerance of the intact fly. Drome-kinin receptor, encoded by the leucokinin receptor gene, LKR, is expressed in DH 44 neurons as well as in stellate cells of the Malpighian tubules. LKR knockdown in DH 44-expressing neurons reduces Malpighian tubule-specific LKR, suggesting interactions between DH 44 and LK signalling pathways. Finally, although a role for DK in desiccation tolerance was not defined, we demonstrate a novel role for Malpighian tubule cell-specific LKR in starvation tolerance. Starvation increases gene expression of epithelial LKR. Also, Malpighian tubule stellate cell-specific knockdown of LKR significantly reduced starvation tolerance, demonstrating a role for neuropeptide signalling during starvation stress.
... 133 JAT DOW \ O §§§ .' U o\ u14>-<.> n\&amp... more ... 133 JAT DOW \ O §§§ .' U o\ u14>-<.> n\>>-' gestion of cellulose 296 Introduction 296 Feeding and body fluid analysis 297 Morphology and ultrastructure 298 Transport 299 Enzymes 300 Organization of gut function 301 10 Conclusion 301 10.1 Classification of the problem ...
ABSTRACT We measured hemolymph Na+ and K+ concentrations, gut Na+ and K+ concentrations, transepi... more ABSTRACT We measured hemolymph Na+ and K+ concentrations, gut Na+ and K+ concentrations, transepithelial electrical potentials (TEPs) and fluxes of Na+, K+ and water for the insectivorous praying mantis Tenodora sinensis (Orthoptera: Mantidae). In addition, we calculated transepithelial potential differences for Na+ (ENa) and K+ (EK). In the mantid, Na+ concentrations were higher in the hemolymph than in the crop, caeca, midgut, ileum, and rectum. Potassium ion concentrations were lower in the hemolymph than in the crop and rectum. All mantid TEPs were lumen negative. The crop TEP was less negative than the TEPs for the anterior and posterior caeca, anterior midgut, posterior midgut, and ileum. Mantid ENa values were all negative and EK values were all positive. Mantid caecal Na+, K+ and water fluxes were all relatively small. These data imply that digestion of insect prey occurs largely in the crop, and the caeca and midgut may not play important roles in digestion. To maintain ionic homeostasis, mantids may actively transport Na+ while passively distributing K+. We discuss these data for mantids in comparison to previous data on the gut function of desert locusts.
SUMMARY 1. Sodium occurs at a much lower electrochemical potential in all gut regions than in the... more SUMMARY 1. Sodium occurs at a much lower electrochemical potential in all gut regions than in the blood. The observed gradients do not decrease with time; the maintenance of the high blood sodium levels therefore requires active uptake against an electrochemical gradient. 2. Potassium occurs at a much higher electrochemical potential in all gut regions than in the blood. The
... 133 JAT DOW \ O §§§ .' U o\ u14>-<.> n\&amp... more ... 133 JAT DOW \ O §§§ .' U o\ u14>-<.> n\>>-' gestion of cellulose 296 Introduction 296 Feeding and body fluid analysis 297 Morphology and ultrastructure 298 Transport 299 Enzymes 300 Organization of gut function 301 10 Conclusion 301 10.1 Classification of the problem ...
Summary 1. Midguts of the larva of the tobacco hornworm larva, Manduca sexta, were isolated, pinn... more Summary 1. Midguts of the larva of the tobacco hornworm larva, Manduca sexta, were isolated, pinned out and double perfused on the stage of an inverted microscope. The pH gradients across the anterior, middle and posterior regions of the gut were measured with a double-barrelled pH microelectrode, simultaneously with electri- cal potentials and the transepithelial potential difference (TEP). 2. The
The NHE family of Na+/H+ exchangers is believed to play an essential role in animals, but may pla... more The NHE family of Na+/H+ exchangers is believed to play an essential role in animals, but may play an additional, specialised epithelial role in insects. The pharmacological sensitivity of the Drosophila melanogaster Malpighian tubule to a range of amiloride derivatives was shown to be consistent with an effect on an exchanger, rather than a Na+ channel. Consistent with this, no
Malpighian tubules are critical organs for epithelial fluid transport and stress tolerance in ins... more Malpighian tubules are critical organs for epithelial fluid transport and stress tolerance in insects, and are under neuroendocrine control by multiple neuropeptides secreted by identified neurons. Here, we demonstrate roles for CRF-like diuretic hormone 44 (DH44) and Drosophila melanogaster kinin (Drome-kinin, DK) in desiccation and starvation tolerance. Gene expression and labelled DH44 ligand binding data, as well as highly selective knockdowns and/or neuronal ablations of DH44 in neurons of the pars intercerebralis and DH44 receptor (DH44-R2) in Malpighian tubule principal cells, indicate that suppression of DH44 signalling improves desiccation tolerance of the intact fly. Drome-kinin receptor, encoded by the leucokinin receptor gene, LKR, is expressed in DH44 neurons as well as in stellate cells of the Malpighian tubules. LKR knockdown in DH44-expressing neurons reduces Malpighian tubule-specific LKR, suggesting interactions between DH44 and LK signalling pathways. Finally, alt...
Malpighian tubules are critical organs for epithelial fluid transport and stress tolerance in ins... more Malpighian tubules are critical organs for epithelial fluid transport and stress tolerance in insects, and are under neuroendocrine control by multiple neuropeptides secreted by identified neurons. Here, we demonstrate roles for CRF-like diuretic hormone 44 (DH 44) and Drosophila melanogaster kinin (Drome-kinin, DK) in desiccation and starvation tolerance. Gene expression and labelled DH 44 ligand binding data, as well as highly selective knockdowns and/or neuronal ablations of DH 44 in neurons of the pars intercerebralis and DH 44 receptor (DH 44-R2) in Malpighian tubule principal cells, indicate that suppression of DH 44 signalling improves desiccation tolerance of the intact fly. Drome-kinin receptor, encoded by the leucokinin receptor gene, LKR, is expressed in DH 44 neurons as well as in stellate cells of the Malpighian tubules. LKR knockdown in DH 44-expressing neurons reduces Malpighian tubule-specific LKR, suggesting interactions between DH 44 and LK signalling pathways. Finally, although a role for DK in desiccation tolerance was not defined, we demonstrate a novel role for Malpighian tubule cell-specific LKR in starvation tolerance. Starvation increases gene expression of epithelial LKR. Also, Malpighian tubule stellate cell-specific knockdown of LKR significantly reduced starvation tolerance, demonstrating a role for neuropeptide signalling during starvation stress.
... 133 JAT DOW \ O §§§ .' U o\ u14>-<.> n\&amp... more ... 133 JAT DOW \ O §§§ .' U o\ u14>-<.> n\>>-' gestion of cellulose 296 Introduction 296 Feeding and body fluid analysis 297 Morphology and ultrastructure 298 Transport 299 Enzymes 300 Organization of gut function 301 10 Conclusion 301 10.1 Classification of the problem ...
ABSTRACT We measured hemolymph Na+ and K+ concentrations, gut Na+ and K+ concentrations, transepi... more ABSTRACT We measured hemolymph Na+ and K+ concentrations, gut Na+ and K+ concentrations, transepithelial electrical potentials (TEPs) and fluxes of Na+, K+ and water for the insectivorous praying mantis Tenodora sinensis (Orthoptera: Mantidae). In addition, we calculated transepithelial potential differences for Na+ (ENa) and K+ (EK). In the mantid, Na+ concentrations were higher in the hemolymph than in the crop, caeca, midgut, ileum, and rectum. Potassium ion concentrations were lower in the hemolymph than in the crop and rectum. All mantid TEPs were lumen negative. The crop TEP was less negative than the TEPs for the anterior and posterior caeca, anterior midgut, posterior midgut, and ileum. Mantid ENa values were all negative and EK values were all positive. Mantid caecal Na+, K+ and water fluxes were all relatively small. These data imply that digestion of insect prey occurs largely in the crop, and the caeca and midgut may not play important roles in digestion. To maintain ionic homeostasis, mantids may actively transport Na+ while passively distributing K+. We discuss these data for mantids in comparison to previous data on the gut function of desert locusts.
SUMMARY 1. Sodium occurs at a much lower electrochemical potential in all gut regions than in the... more SUMMARY 1. Sodium occurs at a much lower electrochemical potential in all gut regions than in the blood. The observed gradients do not decrease with time; the maintenance of the high blood sodium levels therefore requires active uptake against an electrochemical gradient. 2. Potassium occurs at a much higher electrochemical potential in all gut regions than in the blood. The
... 133 JAT DOW \ O §§§ .' U o\ u14>-<.> n\&amp... more ... 133 JAT DOW \ O §§§ .' U o\ u14>-<.> n\>>-' gestion of cellulose 296 Introduction 296 Feeding and body fluid analysis 297 Morphology and ultrastructure 298 Transport 299 Enzymes 300 Organization of gut function 301 10 Conclusion 301 10.1 Classification of the problem ...
Summary 1. Midguts of the larva of the tobacco hornworm larva, Manduca sexta, were isolated, pinn... more Summary 1. Midguts of the larva of the tobacco hornworm larva, Manduca sexta, were isolated, pinned out and double perfused on the stage of an inverted microscope. The pH gradients across the anterior, middle and posterior regions of the gut were measured with a double-barrelled pH microelectrode, simultaneously with electri- cal potentials and the transepithelial potential difference (TEP). 2. The
The NHE family of Na+/H+ exchangers is believed to play an essential role in animals, but may pla... more The NHE family of Na+/H+ exchangers is believed to play an essential role in animals, but may play an additional, specialised epithelial role in insects. The pharmacological sensitivity of the Drosophila melanogaster Malpighian tubule to a range of amiloride derivatives was shown to be consistent with an effect on an exchanger, rather than a Na+ channel. Consistent with this, no
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Papers by Julian Dow