The Reduced Glucose Permeability of the Isolated Malpighian Tubules of the Blowfly Calliphora Vomitoria

1975 ◽  
Vol 62 (2) ◽  
pp. 327-340
Author(s):  
G. KNOWLES
Keyword(s):  
Molecular Weight ◽  
Malpighian Tubule ◽  
Malpighian Tubules ◽  
Glucose Reabsorption ◽  
Glucose Excretion ◽  
Tubule Wall

The excretion of several sugars by the isolated Malpighian tubules of Calliphora vomitoria has been investigated. The isolated tubules do not excrete glucose or trehalose at rates similar to those of sugars of the same molecular weight. Trehalose can be hydrolysed to glucose as it traverses the tubule wall. It is proposed that glucose can be reabsorbed by the tubule. Evidence is presented to suggest that glucose reabsorption can be saturated. Phloridzin was found to increase the rate of glucose excretion by the isolated Malpighian tubule.

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.

scholarly journals Increase in SGLT1-mediated transport explains renal glucose reabsorption during genetic and pharmacological SGLT2 inhibition in euglycemia

2014 ◽  
Vol 306 (2) ◽  
pp. F188-F193 ◽  
Author(s):  
Timo Rieg ◽  
Takahiro Masuda ◽  
Maria Gerasimova ◽  
Eric Mayoux ◽  
Kenneth Platt ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Plasma Concentrations ◽  
Sglt2 Inhibitor ◽  
Double Knockout ◽  
Glucose Reabsorption ◽  
Urinary Glucose ◽  
Sglt2 Inhibition ◽  
Renal Glucose Reabsorption ◽  
Glucose Excretion ◽  
Free Plasma

In the kidney, the sodium-glucose cotransporters SGLT2 and SGLT1 are thought to account for >90 and ∼3% of fractional glucose reabsorption (FGR), respectively. However, euglycemic humans treated with an SGLT2 inhibitor maintain an FGR of 40–50%, mimicking values in Sglt2 knockout mice. Here, we show that oral gavage with a selective SGLT2 inhibitor (SGLT2-I) dose dependently increased urinary glucose excretion (UGE) in wild-type (WT) mice. The dose-response curve was shifted leftward and the maximum response doubled in Sglt1 knockout (Sglt1−/−) mice. Treatment in diet with the SGLT2-I for 3 wk maintained 1.5- to 2-fold higher urine glucose/creatinine ratios in Sglt1−/− vs. WT mice, associated with a temporarily greater reduction in blood glucose in Sglt1−/− vs. WT after 24 h (−33 vs. −11%). Subsequent inulin clearance studies under anesthesia revealed free plasma concentrations of the SGLT2-I (corresponding to early proximal concentration) close to the reported IC50 for SGLT2 in mice, which were associated with FGR of 64 ± 2% in WT and 17 ± 2% in Sglt1−/−. Additional intraperitoneal application of the SGLT2-I (maximum effective dose in metabolic cages) increased free plasma concentrations ∼10-fold and reduced FGR to 44 ± 3% in WT and to −1 ± 3% in Sglt1−/−. The absence of renal glucose reabsorption was confirmed in male and female Sglt1/Sglt2 double knockout mice. In conclusion, SGLT2 and SGLT1 account for renal glucose reabsorption in euglycemia, with 97 and 3% being reabsorbed by SGLT2 and SGLT1, respectively. When SGLT2 is fully inhibited by SGLT2-I, the increase in SGLT1-mediated glucose reabsorption explains why only 50–60% of filtered glucose is excreted.

A Study of the Malpighian Tubules of the Pill Millipede, Glomeris marginata (Villers)

1974 ◽  
Vol 60 (1) ◽  
pp. 41-51
Author(s):  
PATRICIA ANNE FARQUHARSON
Keyword(s):  
Size Distribution ◽  
Fluid Transport ◽  
Molecular Size ◽  
Malpighian Tubules ◽  
Inverse Relation ◽  
Fluid Production ◽  
Molecular Size Distribution ◽  
Molecular Sieving ◽  
Tubule Fluid ◽  
Tubule Wall

1. Tubule fluid:medium ratios (TF/M) have been measured for inulin, glucose, LMWD and HMWD. These TF/M ratios were surprisingly high. 2. The tubule appears to act as a molecular filter; that is to say, molecules move through the tubule wall in inverse relation to their size. This is best illustrated using polyvinyl pyrrolidone as a tracer. The molecular size distribution of PVP fractions present in tubule fluid differs markedly from the molecular size distribution of PVP in the bathing Ringer. 3. No correlation can be made between the inulin and glucose TF/M and the rate of fluid production. However, the inverse relationship between TF/M and rate of fluid production for dextrans indicates a molecular sieving effect. 4. The significance of these results is discussed with reference to models of fluid transport.

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 permeability properties of septate junctions in Malpighian tubules of Rhodnius

1987 ◽  
Vol 88 (2) ◽  
pp. 251-265 ◽  
Author(s):  
H.B. Skaer ◽  
S.H. Maddrell ◽  
J.B. Harrison
Keyword(s):  
Structural Characteristics ◽  
Malpighian Tubule ◽  
Malpighian Tubules ◽  
Septate Junctions ◽  
Blood Sucking ◽  
Effects Of Ph ◽  
Intercellular Clefts ◽  
Luminal Flow ◽  
Tubule Cells ◽  
Positively Charged

This paper describes the structural characteristics and permeability properties of the smooth septate junctions between the upper Malpighian tubule cells of a blood-sucking bug, Rhodnius prolixus. The permeability of the paracellular route was tested only for solutes that could be demonstrated not to cross the epithelium via the cellular route. The intercellular clefts were readily permeated by sucrose, inulin and polyethylene glycol (PEG), showing a higher permeability to molecules of smaller radius (PEG versus sucrose). Negatively charged molecules permeated the clefts more readily than positively charged ones. The effects of pH, urea and luminal flow rate on permeability were studied. The results are discussed in relation to the physiological tightness of the Malpighian tubules to certain solutes and to its function as an excretory epithelium.

scholarly journals Active transport of brilliant blue FCF across the Drosophila midgut and Malpighian tubule epithelia

2019 ◽  
Author(s):  
Dawson B.H. Livingston ◽  
Hirva Patel ◽  
Andrew Donini ◽  
Heath A. MacMillan
Keyword(s):  
Traumatic Injury ◽  
Malpighian Tubule ◽  
Malpighian Tubules ◽  
Brilliant Blue ◽  
Barrier Dysfunction ◽  
Concentration Gradients ◽  
Barrier Disruption ◽  
Brilliant Blue Fcf ◽  
Summary Statement

AbstractUnder conditions of stress, many animals suffer from epithelial barrier disruption that can cause molecules to leak down their concentration gradients, potentially causing a loss of organismal homeostasis, further injury or death. Drosophila is a common insect model, used to study barrier disruption related to aging, traumatic injury, or environmental stress. Net leak of a non-toxic dye (Brilliant blue FCF) from the gut lumen to the hemolymph is often used to identify barrier failure under these conditions, but Drosophila are capable of actively transporting structurally-similar compounds. Here, we examined whether cold stress (like other stresses) causes Brilliant blue FCF (BB-FCF) to appear in the hemolymph of flies fed the dye, and if so whether Drosophila are capable of clearing this dye from their body following chilling. Using in situ midgut leak and transport assays as well as Ramsay assays of Malpighian tubule transport, we tested whether these ionoregulatory epithelia can actively transport BB-FCF. In doing so, we found that the Drosophila midgut and Malpighian tubules can mobilize BB-FCF via an active transcellular pathway, suggesting that elevated concentrations of the dye in the hemolymph may occur from increased paracellular permeability, reduced transcellular clearance, or both.Summary StatementDrosophila are able to actively secrete Brilliant blue FCF, a commonly used marker of barrier dysfunction

Amino-Acid Metabolism in Locust Tissues

1957 ◽  
Vol 34 (2) ◽  
pp. 276-289
Author(s):  
B. A. KILBY ◽  
ELISABETH NEVILLE
Keyword(s):  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Schistocerca Gregaria ◽  
Fat Body ◽  
Malpighian Tubule ◽  
Malpighian Tubules ◽  
Acid Oxidase ◽  
Amino Acid Oxidase ◽  
Mitochondrial Fractions

1. Homogenates of fat-body of Schistocerca gregaria Forsk. were shown to catalyse transamination reactions between α-ketoglutarate and numerous α-amino acids. The aspartate/glutamate and alanine/glutamate transaminases were the most active. They were present in both the ‘soluble’ and the mitochondrial fractions of fat-body cells and also in Malpighian tubules and mid-gut wall. The other transaminases in the fat-body were confined to the mitochondrial fraction. 2. Fat-body, Malpighian tubule and mid-gut wall homogenates were able to convert glutamic acid into glutamine, a compound which could also act as an amino-group donor in some transamination reactions. 3. A glutamate-cytochrome c reductase system which involved diphosphopyridine nucleotide was present in fat-body. 4. Fat-body contained an active arginase, but urease could not be detected. A D-amino-acid oxidase was present, together with a less active L-amino-acid oxidase. 5. In general, it appears that amino-acid metabolism in the locust resembles that in higher animals.

Renal clearance of glucose in hypothermic dogs

1959 ◽  
Vol 196 (4) ◽  
pp. 866-872 ◽  
Author(s):  
G. S. Kanter
Keyword(s):  
Renal Function ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Control Period ◽  
Urine Volume ◽  
Tubular Reabsorption ◽  
Arterial Blood ◽  
Glucose Reabsorption ◽  
Kinetics Of ◽  
Glucose Excretion

Quantitative alterations in both glomerular filtration (GFR) and tubular reabsorption of glucose, before, during and after onset of hypothermia were investigated. Urine was collected by direct cannulation of ureters and arterial blood obtained from a femoral cannula. Creatinine was used to measure GFR and glucose was analyzed by the glucose-oxidase method. During control period (rectal temp. 38°C) it was found that onlg a trace (17 ± 4 mg %) (.09 ± .02 mg/min.) of glucose spilled over into the urine. With the development of hypothermia a progressive fall in glomerular filtration rate was observed (78 ± 5 ml/min. at control rectal temp. (R.T.) to 30 ± 5 ml/min. at R.T. of 25°C). In spite of the fact that less fluid was filtered across the glomerulus, both urine volume and glucose excretion increased markedly (373 ± 122 mg %) (4.3 ± 1.9 mg/min.) at R.T. of 25°C. There is obviously a twofold effect of hypothermia on renal function, physically via the cardiovascular system resulting in a falling GFR and chemically on the tubular reabsorptive processes resulting in a decreased glucose reabsorption. To study the kinetics of this decreased glucose reabsorption, glucose Tm was investigated. It was found that control glucose Tm averaged 380 mg/min. (the E/F ratio being 52%). At 27°C R.T. the Tm was 103 mg/min. (E/F ratio being 73%).

Voltage clamping single cells in intact Malpighian tubules of mosquitoes

2000 ◽  
Vol 279 (4) ◽  
pp. F747-F754 ◽  
Author(s):  
R. Masia ◽  
D. Aneshansley ◽  
W. Nagel ◽  
R. J. Nachman ◽  
K. W. Beyenbach
Keyword(s):  
Apical Membrane ◽  
Single Cells ◽  
Basolateral Membrane ◽  
Malpighian Tubule ◽  
Input Resistance ◽  
Membrane Resistance ◽  
Malpighian Tubules ◽  
Shunt Resistance ◽  
Transport Pathways ◽  
Principal Cells

Principal cells of the Malpighian tubule of the yellow fever mosquito were studied with the methods of two-electrode voltage clamp (TEVC). Intracellular voltage ( V pc) was −86.7 mV, and input resistance ( R pc) was 388.5 kΩ ( n = 49 cells). In six cells, Ba2+ (15 mM) had negligible effects on V pc, but it increased R pc from 325.3 to 684.5 kΩ ( P< 0.001). In the presence of Ba2+, leucokinin-VIII (1 μM) increased V pc to −101.8 mV ( P < 0.001) and reduced R pc to 340.2 kΩ ( P < 0.002). Circuit analysis yields the following: basolateral membrane resistance, 652.0 kΩ; apical membrane resistance, 340.2 kΩ; shunt resistance ( R sh), 344.3 kΩ; transcellular resistance, 992.2 kΩ. The fractional resistance of the apical membrane (0.35) and the ratio of transcellular resistance and R sh (3.53) agree closely with values obtained by cable analysis in isolated perfused tubules and confirm the usefulness of TEVC methods in single principal cells of the intact Malpighian tubule. Dinitrophenol (0.1 mM) reversibly depolarized V pc from −94.3 to −10.7 mV ( P< 0.001) and reversibly increased R pc from 412 to 2,879 kΩ ( P < 0.001), effects that were duplicated by cyanide (0.3 mM). Significant effects of metabolic inhibition on voltage and resistance suggest a role of ATP in electrogenesis and the maintenance of conductive transport pathways.

Cytogenetic analysis of Malpighian tubule polytene chromosomes of Culex pipiens (Diptera: Culicidae)

Genome ◽  
1998 ◽  
Vol 41 (6) ◽  
pp. 751-755 ◽  
Author(s):  
Anna Zambetaki ◽  
Nicole Pasteur ◽  
Penelope Mavragani-Tsipidou
Keyword(s):  
Culex Pipiens ◽  
Polytene Chromosomes ◽  
Malpighian Tubule ◽  
Malpighian Tubules ◽  
Molecular Cytogenetic ◽  
Routine Basis ◽  
Weak Points ◽  
Chromosome Maps ◽  
Global Vector ◽  
Polytene Nuclei

A simple technique is described for obtaining well-spread and readable Malpighian tubule polytene nuclei of Culex pipiens on a routine basis. Detailed polytene chromosome maps are presented with a description of the most prominent landmarks of each chromosome, the regions with asynapsis and the most frequent weak points identified in the polytene arms. Usable Malpighian tubule polytene chromosomes should facilitate molecular cytogenetic, genetic, and potentially biosystematic studies on this medically important global vector of viral inducing encephalitis.Key words: Culex pipiens, polytene chromosomes, Malpighian tubules, banding pattern, photomap.

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