Papers by Klaus Beyenbach
American Journal of Physiology-renal Physiology, 1992
A population of proximal tubules when isolated from the glomerular kidneys of seawater-adapted (S... more A population of proximal tubules when isolated from the glomerular kidneys of seawater-adapted (SW) and freshwater-adapted (FW) killifish (Fundulus heteroclitus) spontaneously secrete fluid. Regardless of SW or FW adaptation, Na and Cl are the dominant electrolytes in secreted fluid. Mg concentrations in fluid secreted by both tubules are significantly greater than those in the peritubular bath, and Mg concentrations are inversely related to Na concentrations. Proximal tubules from either SW or FW fish exhibit low transepithelial voltage (-1 to -2 mV) and low transepithelial resistances (20-30 omega.cm2) typical of other vertebrate proximal tubules. Transepithelial diffusion potentials for Na, Cl, Mg, and SO4 suggest that the paracellular pathway is Na selective and impermeable to divalent ions. Consideration of transepithelial electrochemical potential differences for Na, Cl, Mg, and SO4 suggests active transport of Mg, SO4, and Cl in proximal tubules isolated from SW- and FW-adapted fish. The similarities in the functional properties of secretory proximal tubules isolated from SW- and FW-adapted killifish are striking and raise questions about the in vivo role of these tubules in the renal adaptations to seawater and freshwater.
The Journal of Experimental Biology, Nov 1, 2003
Malpighian tubules, diuresis, diuretic peptide, kinin, leucokinin, intracellular cAMP, intracellu... more Malpighian tubules, diuresis, diuretic peptide, kinin, leucokinin, intracellular cAMP, intracellular Ca 2+ , epithelial Na + channel, Na + /K + /2Cl - cotransport, septate junction, paracellular Cl -conductance.
Kidney & Blood Pressure Research, 1985
The comparative physiology of the renal proximal tubule (PT) is reviewed in the context of verteb... more The comparative physiology of the renal proximal tubule (PT) is reviewed in the context of vertebrate evolution and vertebrate strategies of salt and water balance. Though extrarenal machanisms of salt and water balance contribute importantly to extracellular fluid (ECF) homeostasis in the lower vertebrates, the kidney acquires these functions with evolutionary progress and becomes the dominant organ of ECF homeostasis in mammals. In acquiring the major responsability over the ECF compartment the kidney favored filtration-reabsorption as the preferred mechanism for the rapid turnover of ECF with the advantage of providing quick renal regulatory responses. In spite of this specialization the structure and function of the PT do not appear to have undergone major evolutionary changes. In present-day vertebrates the PT remains as an immensely diverse transport epithelium with impressive capacities for both reabsorptive and secretory work, as exemplified by the mammalian PT with mostly reabsorptive functions and the PT of aglomerular kidneys with mostly secretory functions. The recent evidence for NaCl and fluid secretion in the PT of, unexpectedly, glomerular kidneys is consistant with the functional diversity and the conservative nature of evolution in the case of the PT.
American Journal of Physiology-cell Physiology, Jun 1, 2020
Tetraspanin-2A (Tsp2A) is an integral membrane protein of smooth septate junctions in Drosophila ... more Tetraspanin-2A (Tsp2A) is an integral membrane protein of smooth septate junctions in Drosophila melanogaster. To elucidate its structural and functional roles in Malpighian tubules, we used the c42-GAL4/UAS system to selectively knock down Tsp2A in principal cells of the tubule. Tsp2A localizes to smooth septate junctions (sSJ) in Malpighian tubules in a complex shared with partner proteins Snakeskin (Ssk), Mesh, and Discs large (Dlg). Knockdown of Tsp2A led to the intracellular retention of Tsp2A, Ssk, Mesh, and Dlg, gaps and widening spaces in remaining sSJ, and tumorous and cystic tubules. Elevated protein levels together with diminished V-type H+-ATPase activity in Tsp2A knockdown tubules are consistent with cell proliferation and reduced transport activity. Indeed, Malpighian tubules isolated from Tsp2A knockdown flies failed to secrete fluid in vitro. The absence of significant transepithelial voltages and resistances manifests an extremely leaky epithelium that allows secreted solutes and water to leak back to the peritubular side. The tubular failure to excrete fluid leads to extracellular volume expansion in the fly and to death within the first week of adult life. Expression of the c42-GAL4 driver begins in Malpighian tubules in the late embryo and progresses upstream to distal tubules in third instar larvae, which can explain why larvae survive Tsp2A knockdown and adults do not. Uncontrolled cell proliferation upon Tsp2A knockdown confirms the role of Tsp2A as tumor suppressor in addition to its role in sSJ structure and transepithelial transport.
Journal of Insect Physiology, Nov 1, 1992
In spite of the growing number of in vitro studies conducted with the gypsy moth there are no rep... more In spite of the growing number of in vitro studies conducted with the gypsy moth there are no reports which describe its hemolymph composition. For this reason we have conducted a quantitative analysis of the osmolytes in the hemolymph of the fifth-instar gypsy moth larva reared on a wheat-germ diet. The osmotic pressure of hemolymph is 313 mOsm/kg water and the hemolymph pH is 6.6. The dominant inorganic cations are potassium (29.1 mM), magnesium (25.9 mM), calcium (6.8 mM) and sodium (5.0 mM). The dominant inorganic anions are chloride (14.9 mM), sulfate (12.3 mM), and phosphate (5.7 mM). The electrical conductivity of the hemolymph (4.52 ms/cm) is equivalent to the conductivity of a 98.8 mOsm/kg water NaCl solution. Since the sum of the measured hemolymph cations and anions approaches this osmolality, more than 200 mOsm/kg water of hemolymph solutes are non-electrolytes. Among these non-electrolytes we have identified 18 amino acids (112.0 mM), trehalose (21.1 mM), glucose (2.4 mM) and urea (4.8 mM). Organic solutes such as arginine (0.9 mM), histidine (3.9 mM), lysine (13.9 mM), tyrosine (2.5 mM), aspartic acid (0.3 mM), glutamic acid (1.6 mM), organic phosphates (29.6 mM) and uric acid (0.2 mM) are expected to exist in ionized forms at the hemolymph pH. Together the identified electrolytes and non-electrolytes account for nearly 85% of the measured hemolymph osmolality.
American Journal of Physiology-regulatory Integrative and Comparative Physiology, May 1, 1986
This review attempts to give a retrospective survey of the available evidence concerning the secr... more This review attempts to give a retrospective survey of the available evidence concerning the secretion of NaCl and fluid in renal tubules of the vertebrate kidney. In the absence of glomerular filtration, epithelial secretory mechanisms, which to this date have not been elucidated, are responsible for the renal excretion of NaCl and water in aglomerular fish. However, proximal tubules isolated from glomerular fish kidneys of the flounder, killifish, and the shark also have the capacity to secrete NaCl and fluid. In shark proximal tubules, fluid secretion appears to be driven via secondary active transport of Cl. In another marine vertebrate, the sea snake, secretion of Na (presumably NaCl) and fluid is observed in freshwater-adapted and water-loaded animals. Proximal tubules of mammals can be made to secrete NaCl in vitro together with secretion of aryl acids. An epithelial cell line derived from dog kidney exhibits secondary active secretion of Cl when stimulated with catecholamines. Tubular secretion of NaCl and fluid may serve a variety of renal functions, all of which are considered here. The occurrence of NaCl and fluid secretion in glomerular proximal tubules of teleosts, elasmobranchs, and reptiles and in mammalian renal tissue cultures suggests that the genetic potential for NaCl secretion is present in every vertebrate kidney.
The FASEB Journal, Mar 1, 2008
The Journal of Experimental Biology, Feb 1, 2008
The colony of mosquitoes Aedes aegypti L. was maintained as described previously except for feedi... more The colony of mosquitoes Aedes aegypti L. was maintained as described previously except for feeding larvae with TetraMin TM Tropical Flakes ground manually with mortar and piston. On the day of the experiment a female mosquito (3-7 days post-eclosion) was cold-anesthetized and decapitated. A Malpighian tubule was removed under Ringer solution from its
PLOS ONE, May 29, 2013
Mosquito-borne diseases such as malaria and dengue fever take a large toll on global health. The ... more Mosquito-borne diseases such as malaria and dengue fever take a large toll on global health. The primary chemical agents used for controlling mosquitoes are insecticides that target the nervous system. However, the emergence of resistance in mosquito populations is reducing the efficacy of available insecticides. The development of new insecticides is therefore urgent. Here we show that VU573, a small-molecule inhibitor of mammalian inward-rectifying potassium (Kir) channels, inhibits a Kir channel cloned from the renal (Malpighian) tubules of Aedes aegypti (AeKir1). Injection of VU573 into the hemolymph of adult female mosquitoes (Ae. aegypti) disrupts the production and excretion of urine in a manner consistent with channel block of AeKir1 and renders the mosquitoes incapacitated (flightless or dead) within 24 hours. Moreover, the toxicity of VU573 in mosquitoes (Ae. aegypti) is exacerbated when hemolymph potassium levels are elevated, suggesting that Kir channels are essential for maintenance of whole-animal potassium homeostasis. Our study demonstrates that renal failure is a promising mechanism of action for killing mosquitoes, and motivates the discovery of selective small-molecule inhibitors of mosquito Kir channels for use as insecticides.
Journal of Insect Physiology, Mar 1, 1995
The Journal of Experimental Biology, Jun 1, 2009
Active transepithelial cation transport in insects was initially discovered in Malpighian tubules... more Active transepithelial cation transport in insects was initially discovered in Malpighian tubules, and was subsequently also found in other epithelia such as salivary glands, labial glands, midgut and sensory sensilla. Today it appears to be established that the cation pump is a two-component system of a H + -transporting V-ATPase and a cation/nH + antiporter. After tracing the discovery of the V-ATPase as the energizer of K + /nH + antiport in the larval midgut of the tobacco hornworm Manduca sexta we show that research on the tobacco hornworm V-ATPase delivered important findings that emerged to be of general significance for our knowledge of V-ATPases, which are ubiquitous and highly conserved proton pumps. We then discuss the V-ATPase in Malpighian tubules of the fruitfly Drosophila melanogaster where the potential of post-genomic biology has been impressively illustrated. Finally we review an integrated physiological approach in Malpighian tubules of the yellow fever mosquito Aedes aegypti which shows that the V-ATPase delivers the energy for both transcellular and paracellular ion transport.
The Journal of Experimental Biology, 2019
The small size of Malpighian tubules in the fruit fly Drosophila melanogaster has discouraged mea... more The small size of Malpighian tubules in the fruit fly Drosophila melanogaster has discouraged measurements of the transepithelial electrical resistance. The present study introduces two methods for measuring the transepithelial resistance in isolated D. melanogaster Malpighian tubules using conventional microelectrodes and PClamp hardware and software. The first method uses three microelectrodes to measure the specific transepithelial resistance normalized to tubule length or luminal surface area for comparison with resistances of other epithelia. The second method uses only two microelectrodes to measure the relative resistance for comparing before and after effects in a single Malpighian tubule. Knowledge of the specific transepithelial resistance allows the first electrical model of electrolyte secretion by the main segment of the anterior Malpighian tubule of D. melanogaster. The electrical model is remarkably similar to that of the distal Malpighian tubule of Aedes aegypti when tubules of Drosophila and Aedes are studied in vitro under the same experimental conditions. Thus, despite 189 millions of years of evolution separating these two genera, the electrophysiological properties of their Malpighian tubules remains remarkably conserved.
The oxytocin-arginine-vasopressin family of peptides in invertebrates, J. Proux insect diuretic h... more The oxytocin-arginine-vasopressin family of peptides in invertebrates, J. Proux insect diuretic hormones with homology to Sauvagine/CRF/urotensin, D.A. Schooley peptides in the house cricket, "acheta domesticus" - a possible dual control of malpighian tubules, G.M. Coast et al chemistry and physiology of neuroparsin - an antidiuretic neurohormone of the African locust, J. Girardie and B. Fournier insect adrenocorticotrophic hormone-like diuretic hormone, A. Rafaeli isolation of diuretic factors from head extracts of "formica polyctena", N. De Decker, et al the lepidopteran midgut - a model for Na+-independent solute transport, D.F. Moffett and A. Koch excretion in the house cricket - structural and functional differences between distal and mid-tubules, J.H. Spring and I.S. Kim extracellular fluid homeostasis in insects?, K.W. Beyenbach.
The FASEB Journal, 2009
From the completed genomes of insects it appears that most species possess only two SLC4-like tra... more From the completed genomes of insects it appears that most species possess only two SLC4-like transporters: (i) a Na-driven Cl/HCO3 anion exchanger (NDAE) and (ii) a putative Cl/HCO3 anion exchange...
American Journal of Physiology-Renal Physiology, 1988
A technique is described whereby it is possible to evert a 0.5- to 1.0-mm segment of an amphibian... more A technique is described whereby it is possible to evert a 0.5- to 1.0-mm segment of an amphibian renal tubule and perfuse it in vitro. Consequently, the apical membranes of an intact nephron fragment are directly accessible for electrophysiological study. Viability of the cells of everted diluting segments taken from Ambystoma kidney was indicated by 1) failure of the cells to take up trypan blue and 2) the existence of an apical membrane voltage (average 66 mV, cell negative), which decreased predictably in the presence of either 5 mM barium or elevated potassium in the luminal bathing solution. The utility of the everted tubule to patch clamp studies was tested. A large conductance channel that appeared to be selective for potassium could be demonstrated in a cell-attached patch of the apical membrane of an everted initial collecting tubule. The everted tubule preparation not only provides large quantities of apical membrane for patch clamp studies but, more importantly, allows t...
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 1992
In the course of electrophysiological studies of Malpighian tubules of the mosquito Aedes aegypti... more In the course of electrophysiological studies of Malpighian tubules of the mosquito Aedes aegypti, we have found unusual effects of 2,4-dinitrophenol (DNP) that offer new insights into the electrogenic and conductive properties of the tubule. DNP (10(-4)M) depolarized the basolateral membrane voltage from -58.0 to -3.3 mV, and it depolarized the apical membrane voltage from 110.6 to 8.9 mV. In parallel the transepithelial electrical resistance increased from 11.4 to 16.8 k omega.cm, and the fractional resistance of the apical membrane increased from 0.32 to 0.57. On the assumption that measures of transepithelial resistance in the presence of DNP approach the shunt resistance, the experimental results indicate the following characteristics for the equivalent circuit of the tubule: 1) a shunt resistance that is approximately one-half the transcellular resistance, 2) low and high electromotive forces, respectively, at the basolateral and apical membranes of principal cells, 3) an elec...
American Journal of Physiology-Renal Physiology, 1992
A population of proximal tubules when isolated from the glomerular kidneys of seawater-adapted (S... more A population of proximal tubules when isolated from the glomerular kidneys of seawater-adapted (SW) and freshwater-adapted (FW) killifish (Fundulus heteroclitus) spontaneously secrete fluid. Regardless of SW or FW adaptation, Na and Cl are the dominant electrolytes in secreted fluid. Mg concentrations in fluid secreted by both tubules are significantly greater than those in the peritubular bath, and Mg concentrations are inversely related to Na concentrations. Proximal tubules from either SW or FW fish exhibit low transepithelial voltage (-1 to -2 mV) and low transepithelial resistances (20-30 omega.cm2) typical of other vertebrate proximal tubules. Transepithelial diffusion potentials for Na, Cl, Mg, and SO4 suggest that the paracellular pathway is Na selective and impermeable to divalent ions. Consideration of transepithelial electrochemical potential differences for Na, Cl, Mg, and SO4 suggests active transport of Mg, SO4, and Cl in proximal tubules isolated from SW- and FW-adapt...
Journal of Experimental Zoology, 1982
Previous in vivo clearance studies (Schrock et al., '82) have revealed that taurine is secret... more Previous in vivo clearance studies (Schrock et al., '82) have revealed that taurine is secreted by marine fish kidneys. In the present study taurine secretion by the flounder (Pseudopleuronectes americanus) renal tubule was investigated by assaying the transport of 14C‐taurine in vitro. Collections from isolated fluid‐secreting flounder tubules confirmed the presence of a tubular mechanism for taurine secretion. The flounder renal tubule concentrated taurine in the lumen at a lumen/bath ratio of 25, with the movement across the peritubular membrane identified as the concentrating step of taurine transport. Studies with teased flounder renal tubules identified transport as Na+ and Cl− dependent. Taurine transport was inhibited by β alanine, γ‐aminobutyric acid, and hypotaurine. In a study of the hormonal control of taurine transport, only the adrenal steroid dexamethasone stimulated taurine uptake by the flounder renal tubules. Transport was not affected by the second messengers ...
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Papers by Klaus Beyenbach