INSECT ION HOMEOSTASIS.

1992 ◽  
Vol 172 (1) ◽  
pp. 323-334 ◽  
Author(s):  
W Zeiske
Keyword(s):  
Ion Homeostasis ◽  
Inorganic Ions ◽  
Goblet Cells ◽  
Functional Expression ◽  
Malpighian Tubules ◽  
Cooperative Interaction ◽  
Constant Composition ◽  
Parallel Arrangement ◽  
Graphical Summary ◽  
Ionic Movements

The constant composition of body fluids in insects is maintained by the cooperative interaction of gastrointestinal and urinary tissues. Water follows ionic movements, which are driven by the basolateral Na+/K+-ATPase and/or the apical 'K+(or Na+) pump'. The latter now is thought to be the functional expression of a parallel arrangement of a proton-motive V-ATPase and a K+(or Na+)/nH+ antiport. This review focuses on the pathways for the movement of monovalent inorganic ions through epithelia involved in ion homeostasis. A graphical summary compares the principal findings with respect to cation secretion in lepidopteran caterpillar midgut goblet cells (K+) and in brush-border cells of Malpighian tubules (K+, Na+).

scholarly journals Screening for Modulators of Spermine Tolerance Identifies Sky1, the SR Protein Kinase of Saccharomyces cerevisiae, as a Regulator of Polyamine Transport and Ion Homeostasis

2001 ◽  
Vol 21 (1) ◽  
pp. 175-184 ◽  
Author(s):  
Omri Erez ◽  
Chaim Kahana
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Osmotic Shock ◽  
Ion Homeostasis ◽  
Inorganic Ions ◽  
Yeast Cells ◽  
Wild Type ◽  
Sr Protein ◽  
Polyamine Transport ◽  
Increased Sensitivity

ABSTRACT Although most cells are capable of transporting polyamines, the mechanism that regulates polyamine transport in eukaryotes is still largely unknown. Using a genetic screen for clones capable of restoring spermine sensitivity to spermine-tolerant mutants ofSaccharomyces cerevisiae, we have demonstrated that Sky1p, a recently identified SR protein kinase, is a key regulator of polyamine transport. Yeast cells deleted for SKY1 developed tolerance to toxic levels of spermine, while overexpression of Sky1p in wild-type cells increased their sensitivity to spermine. Expression of the wild-type Sky1p but not of a catalytically inactive mutant restored sensitivity to spermine. SKY1 disruption results in dramatically reduced uptake of spermine, spermidine, and putrescine. In addition to spermine tolerance, sky1Δ cells exhibit increased tolerance to lithium and sodium ions but somewhat increased sensitivity to osmotic shock. The observed halotolerance suggests potential regulatory interaction between the transport of polyamines and inorganic ions, as suggested in the case of the Ptk2p, a recently described regulator of polyamine transport. We demonstrate that these two kinases act in two different signaling pathways. While deletion or overexpression of SKY1 did not significantly affect Pma1p activity, the ability of overexpressed Sky1p, Ptk1p, and Ptk2p to increase sensitivity to LiCl depends on the integrity ofPPZ1 but not of ENA1.

NHE8 mediates amiloride-sensitive Na+/H+exchange across mosquito Malpighian tubules and catalyzes Na+and K+transport in reconstituted proteoliposomes

2007 ◽  
Vol 292 (5) ◽  
pp. F1501-F1512 ◽  
Author(s):  
Wanyoike Kang'ethe ◽  
Karlygash G. Aimanova ◽  
Ashok K. Pullikuth ◽  
Sarjeet S. Gill
Keyword(s):  
Fluid Transport ◽  
Ion Homeostasis ◽  
Malpighian Tubule ◽  
Malpighian Tubules ◽  
Yeast Cells ◽  
Kinetic Properties ◽  
Sodium Load ◽  
Electrophysiological Studies ◽  
Reconstituted Membranes ◽  
Apical Membranes

Following a blood meal, the mosquito Aedes aegypti will have acquired an enormous sodium load that must be rapidly excreted to restore ion homeostasis. It is a process that demands robust sodium and fluid transport capabilities. Even though the identities of the components involved in this ion transport across the mosquito Malpighian tubule epithelia have not been completely determined, electrophysiological studies suggest the contribution of a Na+/H+exchanger extruding cations into the lumen driven secondarily by the proton gradient created by the V-type H+-ATPase in the tubules' apical membrane. We have identified the putative exchanger and designated it AeNHE8. Immunolocalization studies demonstrated that AeNHE8 is expressed in the apical membranes of Malpighian tubules, gastric caecae, and rectum. When heterologously expressed in salt-sensitive yeast cells lacking Na+extrusion and Na+/H+exchange proteins, AeNHE8 rescues the salt-sensitive phenotype and restores the cells' ability to grow in high NaCl media. Furthermore, heterologous expression of AeNHE8 in NHE-deficient fibroblast cells results in an amiloride-sensitive22Na+uptake. To determine the exchanger's kinetic properties, we reconstituted membranes from yeast cells expressing the protein into lipid proteoliposomes and assayed for cation-dependent H+exchange by fluorimetric methods. Our results indicate that AeNHE8 mediates saturable exchange of Na+and K+for H+. We propose that AeNHE8 may be coupled to the inward H+gradient across the Malpighian tubules and plays a role in the extrusion of excess sodium and potassium while maintaining steady intracellular pH in the principal cells.

The Physiology of Excretion in the Cotton Stainer, Dysdercus Fasciatus Signoret

1965 ◽  
Vol 43 (3) ◽  
pp. 523-533
Author(s):  
M. J. BERRIDGE
Keyword(s):  
Amino Acid ◽  
Inorganic Ions ◽  
Close Correlation ◽  
Malpighian Tubules ◽  
High Rate ◽  
Inorganic Ion ◽  
Excessive Intake ◽  
Cotton Stainer ◽  
Potassium Magnesium ◽  
Chloride Concentrations

1. Inorganic excretion has been studied during both phases of excretion. 2. Large amounts of potassium, magnesium and phosphate are excreted during the first phase, but sodium and chloride losses are reduced to a minimum. 3. There is a close correlation between inorganic excretion and the relative abundance of these ions in the diet. 4. The inorganic ion and total nitrogen content of the urine retained in the rectum during the post-excretory phase shows little change. This provides strong evidence for assuming that the Malpighian tubules are inactive during this period. 5. Magnesium, potassium and calcium concentrations in the haemolymph remain relatively constant; sodium and chloride concentrations, however, show a marked increase during the middle of the instar. Amino acid concentration compensates for these changes, so ensuring a constant osmotic pressure in the haemolymph. 6. The high rate of liquid excretion in Dysdercus probably results from an excessive intake of inorganic ions.

scholarly journals The energy requirements of ion homeostasis determine the lifespan of starving bacteria

2021 ◽  
Author(s):  
Severin Josef Schink ◽  
Mark Polk ◽  
Edward Athaide ◽  
Avik Mukherjee ◽  
Constantin Ammar ◽  
...  
Keyword(s):  
Cell Death ◽  
Nutrient Recycling ◽  
Ion Homeostasis ◽  
Inorganic Ions ◽  
Time Lapse ◽  
Growth Conditions ◽  
Medium Composition ◽  
Death Process ◽  
Primary Determinant ◽  
Starvation Survival

The majority of microbes on earth, whether they live in the ocean, the soil or in animals, are not growing, but instead struggling to survive starvation. Some genes and environmental conditions affecting starvation survival have been identified, but despite almost a century of study, we do not know which processes lead to irreversible loss of viability, which maintenance processes counteract them and how lifespan is determined from the balance of these opposing processes. Here, we used time-lapse microscopy to capture and characterize the cell death process of E. coli during carbon starvation for the first time. We found that a lack of nutrients results in the collapse of ion homeostasis, triggering a positive-feedback cascade of osmotic swelling and membrane permeabilization that ultimately results in lysis. Based on these findings, we hypothesized that ion transport is the major energetic requirement for starving cells and the primary determinant of the timing of lysis. We therefore developed a mathematical model that integrates ion homeostasis and cannibalistic nutrient recycling from perished cells to predict lifespan changes under diverse conditions, such as changes of cell size, medium composition, and prior growth conditions. Guided by model predictions, we found that cell death during starvation could be dramatically slowed by replacing inorganic ions from the medium with a non-permeating osmoprotectant, removing the cost of ion homeostasis and preventing lysis. Our quantitative and predictive model explains how survival kinetics are determined in starvation and elucidates the mechanistic underpinnings of starvation survival.

scholarly journals Functional Plasticity of the gut and the Malpighian tubules underlies cold acclimation and mitigates cold-induced hyperkalemia in Drosophila melanogaster

2017 ◽  
Author(s):  
Gil Y. Yerushalmi ◽  
Lidiya Misyura ◽  
Heath A. MacMillan ◽  
Andrew Donini
Keyword(s):  
Water Balance ◽  
Cold Acclimation ◽  
Low Temperatures ◽  
Fluid Transport ◽  
Epithelial Transport ◽  
Ion Homeostasis ◽  
Malpighian Tubule ◽  
Adult Emergence ◽  
Fluid Secretion ◽  
Malpighian Tubules

AbstractAt low temperatures, Drosophila, like most insects, lose the ability to regulate ion and water balance across the gut epithelia, which can lead to a lethal increase of [K+] in the hemolymph (hyperkalemia). Cold-acclimation, the physiological response to low temperature exposure, can mitigate or entirely prevent these ion imbalances, but the physiological mechanisms that facilitate this process are not well understood. Here, we test whether plasticity in the ionoregulatory physiology of the gut and Malpighian tubules of Drosophila may aid in preserving ion homeostasis in the cold. Upon adult emergence, D. melanogaster females were subjected to seven days at warm (25°C) or cold (10°C) acclimation conditions. The cold acclimated flies had a lower critical thermal minimum (CTmin), recovered from chill coma more quickly, and better maintained hemolymph K+ balance in the cold. The improvements in chill tolerance coincided with increased Malpighian tubule fluid secretion and better maintenance of K+ secretion rates in the cold, as well as reduced rectal K+ reabsorption in cold-acclimated flies. To test whether modulation of ion-motive ATPases, the main drivers of epithelial transport in the alimentary canal, mediate these changes, we measured the activities of Na+-K+-ATPase and V-type H+-ATPase at the Malpighian tubules, midgut, and hindgut. Na+/K+-ATPase and V-type H+-ATPase activities were lower in the midgut and the Malpighian tubules of cold-acclimated flies, but unchanged in the hindgut of cold acclimated flies, and were not predictive of the observed alterations in K+ transport. Our results suggest that modification of Malpighian tubule and gut ion and water transport likely prevents cold-induced hyperkalemia in cold-acclimated flies and that this process is not directly related to the activities of the main drivers of ion transport in these organs, Na+/K+- and V-type H+-ATPases.Summary StatementAt low temperatures, insects lose the ability to regulate ion and water balance and can experience a lethal increase in hemolymph [K+]. Previous exposure to low temperatures can mitigate this effect and improve chill tolerance. Here, we show that plasticity of ion and fluid transport across the Malpighian tubule and rectal epithelia likely drive this response.

Fine Structure of the Malpighian Tubules of the Mosquito, Culex pipiens

1971 ◽  
Vol 29 ◽  
pp. 402-403
Author(s):  
Brendan Clifford
Keyword(s):  
Fine Structure ◽  
Culex Pipiens ◽  
Stellate Cell ◽  
Malpighian Tubule ◽  
Cell Types ◽  
Instar Larva ◽  
Malpighian Tubules ◽  
Calliphora Erythrocephala ◽  
Distinct Cell ◽  
Basal Plasma

An ultrastructural investigation of the Malpighian tubules of the fourth instar larva of Culex pipiens was undertaken as part of a continuing study of the fine structure of transport epithelia.Each of the five Malpighian tubules was found to be morphologically identical and regionally undifferentiated. Two distinct cell types, the primary and stellate, were found intermingled along the length of each tubule. The ultrastructure of the stellate cell was previously described in the Malpighian tubule of the blowfly, Calliphora erythrocephala by Berridge and Oschman.The basal plasma membrane of the primary cell is extremely irregular, giving rise to a complex interconnecting network of basal channels. The compartments of cytoplasm entrapped within this system of basal infoldings contain mitochondria, free ribosomes, and small amounts of rough endoplasmic reticulum. The mitochondria are distinctive in that the cristae run parallel to the long axis of the organelle.

Scanning Tunneling Microscopy and Atomic Force Microscopy of Enzymes and Enzyme Complexes

1990 ◽  
Vol 48 (3) ◽  
pp. 174-175
Author(s):  
Ronald D. Edstrom ◽  
Xiuru Yang ◽  
Mary E. Gurnack ◽  
Marcia A. Miller ◽  
Rui Yang ◽  
...  
Keyword(s):  
Cell Biology ◽  
Inorganic Ions ◽  
Bulk Liquid ◽  
Soluble Form ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Metabolic Channeling ◽  
Simplistic Notion ◽  
Soluble Enzymes

Many of the questions in biochemistry and cell biology are concerned with the relationships of proteins and other macromolecules in complex arrays which are responsible for carrying out metabolic sequences. The simplistic notion that the enzymes we isolate in soluble form from the cytoplasm were also soluble in vivo is being replaced by the concept that these enzymes occur in organized systems within the cell. In this newer view, the cytoplasm is organized and the “soluble enzymes” are in fact fixed in the cellular space and the only soluble components of the cell are small metabolites, inorganic ions etc. Further support for the concept of metabolic organization is provided by the evidence of metabolic channeling. It has been shown that for some metabolic pathways, the intermediates are not in free diffusion equilibrium with the bulk liquid in the cell but are passed along, more or less directly, from one enzyme to the next.

The Diagnosis of Lupus Anticoagulants by the Activated Partial Thromboplastin Time - The Central Role of Phosphatidyl Serine

1984 ◽  
Vol 52 (02) ◽  
pp. 172-175 ◽  
Author(s):  
P R Kelsey ◽  
K J Stevenson ◽  
L Poller
Keyword(s):  
Screening Method ◽  
Coagulation Factors ◽  
Phosphatidyl Serine ◽  
Test System ◽  
Specific Factor ◽  
Marginal Effect ◽  
Constant Composition ◽  
Lupus Anticoagulants ◽  
Different Types

SummaryLiposomes of pure phospholipids were used in a modified APTT test system and the role of phosphatidyl serine (PS) in determining the sensitivity of the test system to the presence of lupus anticoagulants was assessed. Six consecutive patients with lupus anticoagulants and seven haemophiliacs with anticoagulants directed at specific coagulation factors, were studied. Increasing the concentration of phospholipid in the test system markedly reduced the sensitivity to lupus anticoagulants but had marginal effect on the specific factor inhibitors. The same effect was achieved when the content of PS alone was increased in a vehicle liposome of constant composition.The results suggest that the lupus anticoagulants can best be detected by a screening method using an APTT test with a reagent of low PS content. The use of a reagent rich in PS will largely abolish the lupus anticoagulant’s effect on the APTT. An approach using the two different types of reagent may facilitate differentiation of lupus inhibitors from other types of anticoagulant.

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