scholarly journals Action of activated 27,000 Mr toxin from Bacillus thuringiensis var. israelensis on Malpighian tubules of the insect, Rhodnius prolixus

1989 ◽  
Vol 94 (3) ◽  
pp. 601-608
Author(s):  
S.H. Maddrell ◽  
J.A. Overton ◽  
D.J. Ellar ◽  
B.H. Knowles
Keyword(s):  
Bacillus Thuringiensis ◽  
Cell Membrane ◽  
Basal Cell ◽  
Time Course ◽  
Fluid Secretion ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Bathing Solution ◽  
Concentrated Solutions ◽  
Intracellular Milieu

The action of activated 27,000 Mr toxin from Bacillus thuringiensis var. israelensis (Bti toxin) on Malpighian tubules of Rhodnius prolixus has been investigated. Its binding to the tubules is slowed by low temperature but is not prevented even at 0 degree C. The binding is less effective at pH 10 than at pH7. Pretreatment of the tubules with 0.1 mmol l-1 ouabain or bumetanide or 1 mumol l-1 5-hydroxytryptamine did not affect the toxicity of the toxin. The toxin causes very large changes in the trans-epithelial potential difference; it changes from 40 mV, lumen negative, often to more than 100 mV, lumen positive. This reflects an initial collapse of the potential of the basal cell membrane, followed by a large positive-going potential change at the luminal cell membrane. Just prior to the effects of the toxin on rapid fluid secretion, the basal cell membrane becomes permeable to sucrose molecules. Raffinose at 170 mmol l-1 in the bathing solution does not protect the tubules from Bti toxin action but dextran, Mr5000, at 60 mmol l-1 significantly delayed failure of fluid secretion and, even more, the onset of staining of the tubule cells with Trypan Blue. Exposing tubules to saline that is calcium-free and/or magnesium-free, or has a composition adjusted to be similar to that of the intracellular milieu, does not affect the time course of failure of fluid secretion induced by the toxin. There is no evidence that effective aggregates of Bti toxin molecules are formed in concentrated solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

Passage of solutes through walls of Malpighian tubules of Rhodnius by paracellular and transcellular routes

1984 ◽  
Vol 246 (5) ◽  
pp. R759-R769 ◽  
Author(s):  
M. J. O'Donnell ◽  
S. H. Maddrell ◽  
B. O. Gardiner
Keyword(s):  
Cell Membrane ◽  
Time Course ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Bathing Medium ◽  
Tubule Cells

The walls of isolated upper Malpighian tubules of the insect, Rhodnius prolixus, are much more permeable to small relatively unchanged solutes (ethanol, xylose, and mannitol) than to larger or more charged solutes (acetate, glycine, tyrosine, and inulin). The more permeable solutes rapidly reach concentrations in the tubule cells equivalent to their concentrations in the bathing medium; the less permeable solutes do not penetrate into the cells. The time course of accumulation of permeable solute in the cells matches the time course of the appearance of solute in the lumen. Substances injected into the hemolymph of fed R. prolixus appear in the urine at concentrations predictable from the permeability of in vitro tubules, supporting the idea that the in vitro permeability of the tubules is representative of their properties in the intact insect. It is suggested that the rapid transcellular penetration of small solutes through the Malpighian tubules reflects the large areas of cell membrane. The area of cell membrane exceeds that of the paracellular clefts by a factor of 10(5).

Anti-diuresis in the blood-feeding insect Rhodnius prolixus Stål: the peptide CAP2b and cyclic GMP inhibit Malpighian tubule fluid secretion.

1997 ◽  
Vol 200 (17) ◽  
pp. 2363-2367 ◽  
Author(s):  
M C Quinlan ◽  
N J Tublitz ◽  
M J O'Donnell
Keyword(s):  
Cyclic Gmp ◽  
Physiological Role ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Blood Feeding ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Tubule Fluid ◽  
Secretion Rates

Rhodnius prolixus eliminates NaCl-rich urine at high rates following its infrequent but massive blood meals. This diuresis involves stimulation of Malpighian tubule fluid secretion by diuretic hormones released in response to distention of the abdomen during feeding. The precipitous decline in urine flow that occurs several hours after feeding has been thought until now to result from a decline in diuretic hormone release. We suggest here that insect cardioacceleratory peptide 2b (CAP2b) and cyclic GMP are part of a novel mechanism of anti-diuresis. Secretion rates of 5-hydroxytryptamine-stimulated Malpighian tubules are reduced by low doses of CAP2b or cyclic GMP. Maximal secretion rates are restored by exposing tubules to 1 mmol l-1 cyclic AMP. Levels of cyclic GMP in isolated tubules increase in response to CAP2b, consistent with a role for cyclic GMP as an intracellular second messenger. Levels of cyclic GMP in tubules also increase as urine output rates decline in vivo, suggesting a physiological role for this nucleotide in the termination of diuresis.

The initial stages in the action of an insecticidal delta-endotoxin of Bacillus thuringiensis var. israelensis on the epithelial cells of the malpighian tubules of the insect, Rhodnius prolixus

1988 ◽  
Vol 90 (1) ◽  
pp. 131-144
Author(s):  
S.H. Maddrell ◽  
N.J. Lane ◽  
J.B. Harrison ◽  
J.A. Overton ◽  
R.B. Moreton
Keyword(s):  
Bacillus Thuringiensis ◽  
Intercellular Junctions ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Ultrastructural Changes ◽  
Cytoplasmic Vacuolization ◽  
Large Numbers ◽  
Delta Endotoxin ◽  
High Concentrations ◽  
Very High

The effects of the 27 X 10(3) Mr insecticidal delta-endotoxin from Bacillus thuringiensis var. israelensis have been studied using, as a model system, isolated insect Malpighian tubules. At all concentrations of the toxin higher than 1 microgram ml-1 (4 X 10(−8) moll-1) applied to the outer surface of the tubules, fluid secretion failed within about 30 min. Except at very high concentrations, where failure always takes at least 30 s, there was an inverse relationship between the concentration of toxin and the time of failure of toxin-treated tubules. During exposure to toxin, the tubules were initially unaffected for a relatively long period and then rapid failure occurred. If the tubules were removed into toxin-free saline just before failure would have occurred, fluid secretion remained normal for at least 2 h, but on return to the origin toxin-containing saline failure was almost immediate. The toxin was found not to bind to the basement membrane. Ultrastructural changes became evident as tubule failure occurred. These initially involved modifications to the basal side of the cells, but later also to the luminal microvilli. Intercellular junctions became disassociated and cytoplasmic vacuolization occurred. The population of intramembranous particles in the basal membranes became reduced with time. Our findings suggest the following hypothesis for the initial stages in the interaction of the toxin with the tubules. Toxin molecules attach to the accessible cell membranes progressively and irreversibly. They do not readily associate by diffusing laterally in the membrane, so that toxic effects develop only when sufficiently large numbers of them attach close together. The molecules may then associate in some way as a complex, perhaps forming a pore in the membrane. Relatively few such pores lead rapidly to cell failure and death.

Serotonin triggers cAMP and PKA-mediated intracellular calcium waves in Malpighian tubules of Rhodnius prolixus

2014 ◽  
Vol 307 (7) ◽  
pp. R828-R836 ◽  
Author(s):  
Paula Gioino ◽  
Brendan G. Murray ◽  
Juan P. Ianowski
Keyword(s):  
Second Messenger ◽  
Fluid Secretion ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Insect Vector ◽  
Excess Water ◽  
Intracellular Ca ◽  
Single Meal ◽  
Hematophagous Insect

Rhodnius prolixus is a hematophagous insect vector of Chagas disease capable of ingesting up to 10 times its unfed body weight in blood in a single meal. The excess water and ions ingested with the meal are expelled through a rapid postprandial diuresis driven by the Malpighian tubules. Diuresis is triggered by at least two diuretic hormones, a CRF-related peptide and serotonin, which were traditionally believed to trigger cAMP as an intracellular second messenger. Recently, calcium has been suggested to act as a second messenger in serotonin-stimulated Malpighian tubules. Thus, we tested the role of calcium in serotonin-stimulated Malpighian tubules from R. prolixus. Our results show that serotonin triggers cAMP-mediated intracellular Ca2+ waves that were blocked by incubation in Ca2+-free saline containing the cell membrane-permeant Ca2+ chelator BAPTA-AM, or the PKA blocker H-89. Treatment with 8-Br-cAMP triggered Ca2+ waves that were blocked by H-89 and BAPTA-AM. Analysis of the secreted fluid in BAPTA-AM-treated tubules showed a 75% reduction in fluid secretion rate with increased K+ concentration, reduced Na+ concentration. Taken together, the results indicate that serotonin triggers cAMP and PKA-mediated Ca2+ waves that are required for maximal ion transport rate.

scholarly journals Fluid Secretion by Malpighian Tubules of Rhodnius prolixus: Neuroendocrine Control With New Insights From a Transcriptome Analysis

2021 ◽  
Vol 12 ◽  
Author(s):  
Ian Orchard ◽  
Jimena Leyria ◽  
Areej Al-Dailami ◽  
Angela B. Lange
Keyword(s):  
Transcriptome Analysis ◽  
Critical Role ◽  
Fluid Secretion ◽  
Rhodnius Prolixus ◽  
G Protein Coupled Receptors ◽  
Malpighian Tubules ◽  
Neuroendocrine Control ◽  
Second Messenger Systems ◽  
Fine Control ◽  
G Protein Coupled

Rhodnius prolixus (the kissing bug and a major vector of Chagas disease) is an obligate blood feeder that in the case of the fifth instar consumes up to 10 times its unfed body weight in a single 20-minute feed. A post-prandial diuresis is initiated, within minutes of the start of gorging, in order to lower the mass and concentrate the nutrients of the meal. Thus, R. prolixus rapidly excretes a fluid that is high in NaCl content and hypo-osmotic to the hemolymph, thereby eliminating 50% of the volume of the blood meal within 3 hours of gorging. In R. prolixus, as with other insects, the Malpighian tubules play a critical role in diuresis. Malpighian tubules are not innervated, and their fine control comes under the influence of the neuroendocrine system that releases amines and neuropeptides as diuretic or antidiuretic hormones. These hormones act upon the Malpighian tubules via a variety of G protein-coupled receptors linked to second messenger systems that influence ion transporters and aquaporins; thereby regulating fluid secretion. Much has been discovered about the control of diuresis in R. prolixus, and other model insects, using classical endocrinological studies. The post-genomic era, however, has brought new insights, identifying novel diuretic and antidiuretic hormone-signaling pathways whilst also validating many of the classical discoveries. This paper will focus on recent discoveries into the neuroendocrine control of the rapid post-prandial diuresis in R. prolixus, in order to emphasize new insights from a transcriptome analysis of Malpighian tubules taken from unfed and fed bugs.

Intracellular ion activities in Malpighian tubule cells ofRhodnius prolixus: evaluation of Na+-K+-2Cl-cotransport across the basolateral membrane

2002 ◽  
Vol 205 (11) ◽  
pp. 1645-1655 ◽  
Author(s):  
Juan P. Ianowski ◽  
Robert J. Christensen ◽  
Michael J. O'Donnell
Keyword(s):  
Basolateral Membrane ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Rhodnius Prolixus ◽  
Passive Movement ◽  
Malpighian Tubules ◽  
Intracellular Ion Activities ◽  
Ion Activities ◽  
Tubule Cells ◽  
Electrochemical Potentials

SUMMARYIntracellular ion activities (aion) and basolateral membrane potential (Vbl) were measured in Malpighian tubule cells of Rhodnius prolixus using double-barrelled ion-selective microelectrodes. In saline containing 103mmoll-1Na+, 6mmoll-1 K+ and 93mmoll-1Cl-, intracellular ion activities in unstimulated upper Malpighian tubules were 21, 86 and 32mmoll-1, respectively. In serotonin-stimulated tubules, aCl was unchanged, whereas aNa increased to 33mmoll-1 and aK declined to 71mmoll-1. Vbl was -59mV and -63mV for unstimulated and stimulated tubules, respectively. Calculated electrochemical potentials(Δμ/F) favour passive movement of Na+ into the cell and passive movement of Cl- out of the cell in both unstimulated and serotonin-stimulated tubules. Passive movement of K+ out of the cell is favoured in unstimulated tubules. In stimulated tubules, Δμ/F for K+ is close to 0 mV.The thermodynamic feasibilities of Na+-K+-2Cl-, Na+-Cl-and K+-Cl- cotransporters were evaluated by calculating the net electrochemical potential (Δμnet/F) for each transporter. Our results show that a Na+-K+-2Cl- or a Na+-Cl- cotransporter but not a K+-Cl- cotransporter would permit the movement of ions into the cell in stimulated tubules. The effects of Ba2+ and ouabain on Vbl and rates of fluid and ion secretion show that net entry of K+ through ion channels or the Na+/K+-ATPase can be ruled out in stimulated tubules. Maintenance of intracellular Cl- activity was dependent upon the presence of both Na+ and K+ in the bathing saline. Bumetanide reduced the fluxes of both Na+ and K+. Taken together, the results support the involvement of a basolateral Na+-K+-2Cl- cotransporter in serotonin-stimulated fluid secretion by Rhodnius prolixus Malpighian tubules.

The regulation of haemolymph potassium activity during initiation and maintenance of diuresis in fed Rhodnius prolixus

1993 ◽  
Vol 177 (1) ◽  
pp. 273-285 ◽  
Author(s):  
S. H. Maddrell ◽  
M. J. O'Donnell ◽  
R. Caffrey
Keyword(s):  
Opposite Direction ◽  
Major Element ◽  
Potassium Concentration ◽  
Fluid Secretion ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Blood Sucking ◽  
Potassium Absorption ◽  
Stimulation Of

The blood-sucking insect Rhodnius prolixus rapidly eliminates a Na(+)-rich K(+)-poor urine after its large meals. K(+)-rich fluid is first secreted by the upper Malpighian tubules and passes to the lower tubules where most of the potassium is reabsorbed. During the initial stimulation of the tubules, the lower tubules must be activated first to avoid loss of potassium. The major element in this is that they respond more rapidly than do the upper tubules to particular hormonal concentrations rather than that they react to lower hormonal concentrations than do the upper tubules. During subsequent diuresis, regulation of the haemolymph potassium concentration depends on three cooperative homoeostatic mechanisms in the tubules. A fall in potassium concentration of the medium bathing the tubules causes (i) a decrease in the rate of fluid secretion by the upper tubules, (ii) a decrease in potassium concentration in the fluid secreted by the upper tubules and (iii) an increase in the rate of potassium absorption by the lower tubules. The tubules respond in the opposite direction to an increase in potassium concentration of the medium. As a result, the potassium concentration of the urine can be adjusted to match the potassium concentration of the fluids absorbed from the gut, so that the potassium concentration of the insect's haemolymph remains unaltered.

Analysis of epithelial transport by measurement of K+, Cl- and pH gradients in extracellular unstirred layers: ion secretion and reabsorption by Malpighian tubules of Rhodnius prolixus

1997 ◽  
Vol 200 (11) ◽  
pp. 1627-1638 ◽  
Author(s):  
KA Collier ◽  
MJ O'Donnell
Keyword(s):  
Epithelial Transport ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Unstirred Layer ◽  
Ph Gradients ◽  
In Situ Preparation

Summary The pH and concentrations of K+ and Cl- in the unstirred layer (USL) associated with the basolateral surfaces of the upper and lower Malpighian tubules of Rhodnius prolixus were measured using extracellular ion-selective microelectrodes. When stimulated with 5-hydroxytryptamine (5-HT) in vitro, the upper Malpighian tubule secretes Na+, K+, Cl- and water at high rates; the lower Malpighian tubule reabsorbs K+ and Cl- but not water. Concentrations of K+ and Cl- in the unstirred layer of the lower Malpighian tubule ([K+]USL, [Cl-]USL) were greater than those in the bathing saline, consistent with the accumulation of K+ and Cl- in the USL during 5-HT-stimulated KCl reabsorption. [K+]USL exceeded [K+]Bath by as much as 5.3-fold. Calculations of K+ flux based on measurements of [K+]USL at various distances from the tubule surface agreed well with flux calculated from the rate of fluid secretion and the change in K+ concentration of the secreted fluid during passage through the lower tubule. Concentrations of K+ in the unstirred layer of the upper Malpighian tubule were reduced relative to those in the bathing saline, consistent with depletion of K+ from the USL during 5-HT-stimulated secretion of K+ from bath to lumen. Changes in [K+]USL during 5-HT-stimulated K+ secretion from single upper Malpighian tubule cells could be resolved. Although differences between [K+]USL and [K+]Bath were apparent for upper and lower tubules in an in situ preparation, they were reduced relative to the differences measured using isolated tubules. We suggest that convective mixing of the fluids around the tubules by contractions of the midgut and hindgut reduces, but does not eliminate, differences between [K+]USL and [K+]Bath in situ. The USL was slightly acidic relative to the bath in 5-HT-stimulated upper and lower tubules; contributions to USL acidification are discussed. The results also show that the techniques described in this paper can resolve rapid and localized changes in ion transport across different regions of Malpighian tubules in response to stimulants or inhibitors of specific membrane transporters.

scholarly journals ELECTRON MICROSCOPE STUDIES ON THE CELLS OF THE MALPIGHIAN TUBULES OF THE GRASSHOPPER (ORTHOPTERA, ACRIDIDAE)

1955 ◽  
Vol 1 (3) ◽  
pp. 197-202 ◽  
Author(s):  
H. W. Beams ◽  
T. N. Tahmisian ◽  
R. L. Devine
Keyword(s):  
Electron Microscope ◽  
Cell Membrane ◽  
Cell Body ◽  
Basal Cell ◽  
Brush Border ◽  
Malpighian Tubules ◽  
Cell Cytoplasm ◽  
Small Bodies ◽  
Dense Cores ◽  
Basal Zone

For purposes of description, the cells of the Malpighian tubules of the grasshopper may be divided into basal, intermediate, and apical zones. The basal zone of the cell contains what appears to be an elaborate infolding of the cell membrane at the base. This condition results in the basal cell cytoplasm being divided into many compartments. The compartments contain mitochondria that are often arranged in rows. Other small bodies which possess relatively dense outer borders and less dense cores were observed within the compartments. These bodies are unidentified. The brush border of the apical zone contains a multitude of vertically arranged protoplasmic processes. Stages were found which suggest that the filamentous mitochondria migrate from the cell body to the base of the protoplasmic processes, where they enter them and move apically. Some of the mitochondria were observed at the very tips of the processes where they enlarge producing an accompanying bulging of the tips. This condition is interpreted as a stage in the pinching off of the mitochondria-laden tips of the protoplasmic processes.

Active transport of sodium by the malpighian tubules of the tsetse fly Glossian morsitans

1976 ◽  
Vol 64 (2) ◽  
pp. 357-368
Author(s):  
J. D. Gee
Keyword(s):  
Cell Function ◽  
Malpighian Tubule ◽  
Active Role ◽  
Fluid Secretion ◽  
Sodium Concentration ◽  
Tsetse Fly ◽  
Malpighian Tubules ◽  
Bathing Solution ◽  
Bathing Medium

Isolated Malpighian tubules of Glossina morsitans are able to transport sodium against its concentration gradient. Their rate of secretion is dependent on the sodium concentration of the bathing medium. Potassium must be present in the bathing solution for rapid secretion to be maintained, but it does not play an active role in fluid secretion. Lithium and ammonium ions are able to substitute partially for sodium, other monovalent cations cannot. Ouabain does not affect rapid secretion by Glossina tubules in vitro. Conclusions drawn from the results are incorporated into a model of Malpighian tubule cell function in this insect.

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