scholarly journals Physiological and structural maturation of a polarised epithelium: the Malpighian tubules of a blood-sucking insect, Rhodnius prolixus

1990 ◽  
Vol 96 (3) ◽  
pp. 537-547
Author(s):  
H. LE B. SKAER ◽  
J. B. HARRISON ◽  
S. H. P. MADDRELL
Keyword(s):  
Fluid Transport ◽  
Physiological Function ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Second Phase ◽  
Structural Development ◽  
Blood Sucking ◽  
Late Embryogenesis ◽  
Intercellular Contacts ◽  
Two Phases

The development of polarity in a simple epithelium, the Malpighian tubules of Rhodnius, is analysed both ultrastructurally and physiologically. The onset of physiological function, including fluid secretion and the transport of solutes, is determined in late embryos and young hatchling insects and compared with structural development in tubules over a similar period. Two phases of maturation, separated by several days, are detected. The first, during late embryogenesis, involves the development of mature intercellular contacts and the dilation of the lumen, and is associated with the ability to transport specific solutes. The second phase involves the elaboration of the apical and basal membranes and the generation of mitochondria, and is associated with the onset of fluid transport in the tubules and with feeding in 4-day-old hatchlings.

THE EFFECTS OF MANDUCA SEXTA DIURETIC HORMONE ON FLUID TRANSPORT BY THE MALPIGHIAN TUBULES AND CRYPTONEPHRIC COMPLEX OF MANDUCA SEXTA

1993 ◽  
Vol 178 (1) ◽  
pp. 231-243 ◽  
Author(s):  
N. Audsley ◽  
G. M. Coast ◽  
D. A. Schooley
Keyword(s):  
Cyclic Amp ◽  
Manduca Sexta ◽  
Fluid Transport ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Hormonal Control ◽  
Malpighian Tubules ◽  
Proximal Tubules ◽  
Fluid Absorption ◽  
Diuretic Hormone

1. Manduca sexta diuretic hormone (Mas-DH) stimulates fluid secretion by adult Malpighian tubules of M. sexta, demonstrating its site of diuretic action in M. sexta for the first time. It was not possible to develop a suitable bioassay to measure fluid secretion in larval proximal tubules. 2. Mas-DH has an antidiuretic action on the cryptonephric complex of larval M. sexta because it increases fluid absorption from the rectum. It appears that in this complex Mas-DH is acting on a Na+/K+/2Cl- co-transporter, presumably on the basal membrane of the cryptonephric Malpighian tubules, because Mas-DH-stimulated fluid absorption by the cryptonephric complex is inhibited by bumetanide or the removal of Cl-, Na+ or K+ from the haemolymph side of the tissue. This is the first demonstration of hormonal control of fluid absorption by the cryptonephric complex. 3. Concomitant with the stimulation of fluid transport, Mas-DH increases the amount of cyclic AMP secreted by adult Malpighian tubules and the cryptonephric complex. In addition, Mas-DH promotes cyclic AMP production by the larval proximal 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.

scholarly journals SYNERGISM OF HORMONES CONTROLLING EPITHELIAL FLUID TRANSPORT IN AN INSECT

1993 ◽  
Vol 174 (1) ◽  
pp. 65-80 ◽  
Author(s):  
S. H. P. Maddrell ◽  
W. S. Herman ◽  
J. A. Farndale ◽  
J A Riegel
Keyword(s):  
Adenylate Cyclase ◽  
Fluid Transport ◽  
Fluid Secretion ◽  
Rapid Onset ◽  
Threshold Concentration ◽  
Malpighian Tubules ◽  
Dependent Manner ◽  
Response Curves ◽  
Diuretic Hormone ◽  
Dose Dependent

Forskolin stimulates rapid fluid secretion by the Malpighian tubules of Rhodnius prolixus at concentrations above 5x10–6 mol l-1. In the presence of a threshold concentration of forskolin, the tubules are 30–50 times more sensitive to 5-hydroxytryptamine (5-HT) than in its absence. Similar synergism is seen between 5-HT and extracts of the mesothoracic ganglionic mass (which is rich in the peptide diuretic hormone, DH) and between 5-HT and samples of haemolymph, also rich in peptide DH, from fed insects 1–2 h after feeding. The dose-response curves for mixtures of forskolin and 5-HT and of peptide DH and 5-HT are all very steep, approximately five times steeper than for any one stimulant alone. Forskolin, 5-HT and extracts of the ganglionic mass all stimulated adenylate cyclase from broken membrane preparations from the Malpighian tubules in a dose-dependent manner and at doses similar to those required to stimulate fluid secretion by intact tubules. Mixtures of ganglionic extract and 5- HT stimulated adenylate cyclase activity in a synergistic fashion. Injections into fifth-instar Rhodnius, 24 h before feeding, of 5,7-dihydroxytryptamine, which is known to block or reduce 5-HT release, caused delays in the onset of the consequent diuresis or prevented it altogether. This is consistent with the proposal that the rapid onset of diuresis after feeding is caused by the simultaneous release of 5-HT and peptide DH acting synergistically.

Calcium entry in rat parotid acini: activation by carbachol and aluminum fluoride

1990 ◽  
Vol 258 (4) ◽  
pp. C654-C661 ◽  
Author(s):  
L. M. Mertz ◽  
V. J. Horn ◽  
B. J. Baum ◽  
I. S. Ambudkar
Keyword(s):  
Fluid Transport ◽  
Fluid Secretion ◽  
Transient Increase ◽  
Protein Activation ◽  
Initial Transient ◽  
Entry Pathway ◽  
G Protein Activation ◽  
Rat Parotid ◽  
Two Phases ◽  
Sustained Increase

Entry of extracellular Ca2+ into the cytosol of exocrine cells plays an important role in the process of fluid transport, especially during periods of prolonged secretion. However, in parotid acinar cells, the process of Ca2+ entry and the identity of factors which regulate it remain obscure. In this report, we demonstrate that AlF-4, like carbachol, activates Ca2+ entry into dispersed rat parotid acini. In physiological Ca2(+)-containing (1.28 mM) medium, both agents elicit three phases of cytosolic Ca2+ change, an initial transient increase (intracellular Ca2+ dependent) followed sequentially by a decrease (intra- and extracellular Ca2+ dependent) and a small sustained increase (extracellular Ca2+ dependent). Cytosolic Ca2+ concentration ([Ca2+]i) during the last two phases is influenced by variations in extracellular [Ca2+]. Elevation of extracellular [Ca2+], at any time after the initial transient increase, results in a rise of cytosolic [Ca2+], thus demonstrating the existence of a Ca2+ entry pathway during the two later phases. These data suggest the likelihood that in parotid acini, G protein activation is involved in stimulating this Ca2+ entry pathway. Because in AlF-4-treated acini entry into the cytosol is detectable only after the initial intracellular Ca2+ release phase, we suggest that this Ca2+ entry process does not accompany initial intracellular Ca2+ mobilization. Furthermore, the sustained cytosolic [Ca2+] elevation which can be observed 15-30 min after initial stimulation of acini is likely determined by this Ca2+ entry process which, in physiological conditions, could support sustained fluid secretion.

Stimulation of sodium transport and fluid secretion by ouabain in an insect malpighian tubule

1988 ◽  
Vol 137 (1) ◽  
pp. 265-276 ◽  
Author(s):  
S. H. Maddrell ◽  
J. A. Overton
Keyword(s):  
Fluid Flow ◽  
Sodium Transport ◽  
Fluid Transport ◽  
Electrical Potential ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Sodium Ions ◽  
Tubule Cells ◽  
Stimulation Of

Ouabain, at all concentrations higher than 2 × 10(−7) mol l-1, stimulates the rate at which the Malpighian tubules of the insect, Rhodnius, transport sodium ions and fluid into the lumen. An effect on paracellular movement of sodium ions is unlikely because ouabain makes the electrical potential of the lumen more positive, which would slow diffusion of sodium into the lumen. Radioactive ouabain binds to the haemolymph-facing sides of the tubule cells but not to the luminal face. This binding is reduced in the presence of elevated levels of potassium or of non-radioactive ouabain. Bound ouabain is only slowly released on washing in ouabain-free saline. The evidence suggests that there is a Na+/K+-ATPase on the outer (serosal) membranes of the tubules. Such a pump would transport sodium in a direction opposed to the flow of ions and water involved in fluid transport; poisoning it with ouabain would remove this brake, and fluid flow and sodium transport would increase, as observed.

Fluid secretion and microvillar ultrastructure in mosquito malpighian tubules

1989 ◽  
Vol 257 (5) ◽  
pp. R1096-R1102
Author(s):  
T. J. Bradley ◽  
C. Snyder
Keyword(s):  
Fluid Transport ◽  
Fluid Secretion ◽  
Blood Feeding ◽  
Malpighian Tubules ◽  
Primary Cells ◽  
Ultrastructural Examination ◽  
Aedes Taeniorhynchus ◽  
Physiological Limit ◽  
Secretion Rates

The Malpighian tubules of fourth instar larvae, pupae, and female adults of the mosquito Aedes taeniorhynchus were examined with regard to in vitro fluid secretion rate and the ultrastructural features of the microvillar border of the primary cells. In vitro fluid secretion rates were determined after stimulation with 5-hydroxytryptamine. While larval tubules are capable of rapid fluid secretion, the tubules of pupae exhibit very low rates of secretion, indistinguishable from 0 nl/h. The capacity to secrete fluid returns after the pupal-adult molt and is further enhanced after blood feeding. Similar results were obtained in tubules stimulated in vitro with dibutyryl adenosine 3',5'-cyclic monophosphate. Ultrastructural examination of the microvillar border of the primary cells of the Malpighian tubules revealed that the period of reduced secretion capacity in the pupal tubules is correlated with a marked reduction in microvillar volume, microvillar surface area, and mitochondrial content in the microvillar border. The results suggest that microvilli of a certain size and containing extensions of mitochondria are required for rapid fluid transport. The absence of these conditions in pupal tubules cannot be overcome by in vitro stimulation with known secretagogues and therefore represents a physiological limit on transport performance in the pupal tubules of mosquitoes.

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.

Accurate Detection and Quantization of Leaf- Diseases through Soft Computing

2018 ◽  
Vol 1 (1) ◽  
pp. 236-247
Author(s):  
Divya Srivastava ◽  
Rajitha B. ◽  
Suneeta Agarwal
Keyword(s):  
Machine Learning ◽  
Image Processing ◽  
Agricultural Production ◽  
Bacterial Blight ◽  
Early Stage ◽  
Second Phase ◽  
Computationally Efficient ◽  
Stage Of Disease ◽  
Accurate Detection ◽  
Two Phases

Diseases in leaves can cause the significant reduction in both quality and quantity of agricultural production. If early and accurate detection of disease/diseases in leaves can be automated, then the proper remedy can be taken timely. A simple and computationally efficient approach is presented in this paper for disease/diseases detection on leaves. Only detecting the disease is not beneficial without knowing the stage of disease thus the paper also determine the stage of disease/diseases by quantizing the affected of the leaves by using digital image processing and machine learning. Though there exists a variety of diseases on leaves, but the bacterial and fungal spots (Early Scorch, Late Scorch, and Leaf Spot) are the most prominent diseases found on leaves. Keeping this in mind the paper deals with the detection of Bacterial Blight and Fungal Spot both at an early stage (Early Scorch) and late stage (Late Scorch) on the variety of leaves. The proposed approach is divided into two phases, in the first phase, it identifies one or more disease/diseases existing on leaves. In the second phase, amount of area affected by the disease/diseases is calculated. The experimental results obtained showed 97% accuracy using the proposed approach.

Representação e simbolismo: artes visuais na fronteira Brasil/Bolívia

2020 ◽  
Vol 4 (3) ◽  
pp. 286
Author(s):  
Paulo César Antonini de Souza ◽  
Derick Trindade Bezerra
Keyword(s):  
Visual Arts ◽  
Social Order ◽  
Research Field ◽  
Border Region ◽  
Second Phase ◽  
Two Dimensional ◽  
Santa Cruz ◽  
Cultural Conditions ◽  
Two Phases ◽  
America Latina

ResumoTendo por campo de investigação o Festival da América do Sul Pantanal (FASP) em 2018, na cidade de Corumbá (Brasil), objetiva-se identificar a materialidade e conceitos que permeiam as manifestações artísticas bidimensionais nesta região de fronteira, a partir da percepção de artistas da Bolívia. A pesquisa se organizou em duas fases: na primeira foi realizado um levantamento em plataformas online de produções acadêmicas em artes visuais, com foco no trabalho bidimensional, utilizando os descritores “arte popular” e “estética latina” resultando em três artigos. Na segunda fase foram selecionados dois trabalhos de uma artista da Bolívia, participante da mostra “Conexão Santa Cruz”, realizada durante o FASP 2018, que foram analisados em seus níveis representacional e simbólico. Pela interpretação das imagens foi possível construir uma leitura sobre a perspectiva da artista a respeito de suas condições culturais dentro da ordenação social em que se encontra situada.Palavras-chave: Artes Visuais. Arte Popular. Arte Regional. América Latina. Representation and symbolism: visual arts on the Brazil/Bolivia frontierAbstractHaving as research field the Festival da América do Sul Pantanal (FASP) in 2018, in the city of Corumbá (Brazil), the objective is to identify the materiality and concepts that permeate the two-dimensional artistic manifestations in this border region, from the perception of artists from Bolivia. The research was organized in two phases: in the first, a survey was carried out on online platforms of academic productions in visual arts, focusing on two-dimensional work, using the descriptors “arte popular” and “estética latina” resulting in three articles. In the second phase, two works were selected by an artist from Bolivia, participating in the exhibition “Conexão Santa Cruz”, held during FASP 2018, which were analyzed at their representational and symbolic levels. Through the interpretation of the images, it was possible to construct a reading on the artist’s perspective regarding her cultural conditions within the social order in which she is located.Keywords: Visual Arts. Folk Art. Regional Art. Latin America.Representación y simbolismo: artes visuales en la frontera de Brasil/BoliviaResumenTeniendo como campo de investigación el Festival de Sudamérica Pantanal (FASP) en 2018, en la ciudad de Corumbá (Brasil), el objetivo es identificar la materialidad y conceptos que permean las manifestaciones artísticas bidimensionales en esta región fronteriza, desde la percepción de artistas de Bolivia. La investigación se organizó en dos fases: en la primera, se realizó una encuesta en plataformas online de producciones académicas en artes visuales, con foco en el trabajo bidimensional, utilizando los descriptores “arte popular” y “estética latina” dando como resultado tres artículos. En la segunda fase, dos obras fueron seleccionadas por un artista de Bolivia, participante de la exposición “Conexão Santa Cruz”, realizada durante FASP 2018, que fueron analizadas en sus niveles representativos y simbólicos. A través de la interpretación de las imágenes, fue posible construir una lectura sobre la perspectiva de la artista sobre sus condiciones culturales dentro del orden social en el que se ubica.Palabras clave: Artes Visuales. Arte Popular. Arte Regional. América Latina.

scholarly journals Development and validation of a short version of the Sarcopenia Quality of Life questionnaire: the SF-SarQoL

2021 ◽  
Author(s):  
A. Geerinck ◽  
C. Beaudart ◽  
J.-Y. Reginster ◽  
M. Locquet ◽  
C. Monseur ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Short Form ◽  
Reduction Process ◽  
Community Dwelling ◽  
Short Version ◽  
Second Phase ◽  
Life Questionnaire ◽  
Quality Of Life Questionnaire ◽  
Two Phases

Abstract Purpose To facilitate the measurement of quality of life in sarcopenia, we set out to reduce the number of items in the previously validated Sarcopenia Quality of Life (SarQoL®) questionnaire, and to evaluate the clinimetric properties of this new short form. Methods The item reduction process was carried out in two phases. First, information was gathered through item-impact scores from older people (n = 1950), a Delphi method with sarcopenia experts, and previously published clinimetric data. In the second phase, this information was presented to an expert panel that decided which of the items to include in the short form. The newly created SFSarQoL was then administered to older, community-dwelling participants who previously participated in the SarcoPhAge study. We examined discriminative power, internal consistency, construct validity, test–retest reliability, structural validity and examined item parameters with a graded response model (IRT). Results The questionnaire was reduced from 55 to 14 items, a 75% reduction. A total of 214 older, community-dwelling people were recruited for the validation study. The clinimetric evaluation showed that the SF-SarQoL® can discriminate on sarcopenia status [EWGSOP2 criteria; 34.52 (18.59–43.45) vs. 42.86 (26.56–63.69); p = 0.043], is internally consistent (α = 0.915, ω = 0.917) and reliable [ICC = 0.912 (0.847–0.942)]. A unidimensional model was fitted (CFI = 0.978; TLI = 0.975; RMSEA = 0.108, 90% CI 0.094–0.123; SRMR = 0.055) with no misfitting items and good response category separation. Conclusions A new, 14-item, short form version of the Sarcopenia Quality of Life questionnaire has been developed and shows good clinimetric properties.

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