scholarly journals Intracellular electrical potential measurements in Drosophila follicles

1986 ◽  
Vol 81 (1) ◽  
pp. 207-221 ◽  
Author(s):  
J. Bohrmann ◽  
E. Huebner ◽  
K. Sander ◽  
H. Gutzeit
Keyword(s):  
Juvenile Hormone ◽  
Developmental Stages ◽  
Electrical Potential ◽  
Potential Difference ◽  
Published Data ◽  
Nurse Cells ◽  
Electrical Field ◽  
Positive Potential ◽  
Calculated Length ◽  
Significant Potential

We measured the intracellular electrical potential in oocyte and nurse cells of Drosophila follicles at different developmental stages (6–14) and determined the intrafollicular potential difference. During stages 8–10B, when intrafollicular transport is known to occur, no significant potential difference was found. During late vitellogenic stages the nurse cells assume a more positive potential than the oocyte. This result contrasts with the published data on Hyalophora follicles, in which intercellular electrophoresis of negatively charged proteins occurs from nurse cells to oocyte as a result of an intrafollicular potential difference (nurse cells more negative than the oocyte). Such a potential difference was not observed in Drosophila follicles at any stage, not even after application of juvenile hormone. The extrafollicular electrical field is described with a dipole model. The hypothetical dipole is located in the long axis of the follicle and changes its calculated length stage-specifically.

The extracellular electrical current pattern and its variability in vitellogenic Drosophila follicles

1986 ◽  
Vol 81 (1) ◽  
pp. 189-206 ◽  
Author(s):  
J. Bohrmann ◽  
A. Dorn ◽  
K. Sander ◽  
H. Gutzeit
Keyword(s):  
Juvenile Hormone ◽  
Current Density ◽  
Developmental Stages ◽  
Electrical Current ◽  
Posterior Pole ◽  
The Other ◽  
Follicular Epithelium ◽  
Nurse Cells ◽  
Vibrating Probe ◽  
Current Pattern

We determined the extracellular electrical current pattern around Drosophila follicles at different developmental stages (7–14) with a vibrating probe. At most stages a characteristic pattern can be recognized: current leaves near the oocyte end of the follicle and enters at the nurse cells. Only at late vitellogenic stages was an inward-directed current located at the posterior pole of many follicles. Most striking was the observed heterogeneity both in current pattern and in current density between follicles of the same stage. Different media (changed osmolarity or pH, addition of cytoskeletal inhibitors or juvenile hormone) were tested for their effects on extrafollicular currents. The current density was consistently influenced by the osmolarity of the medium but not by the other parameters tested. Denuded nurse cells (follicular epithelium locally stripped off) show current influx, while an accidentally denuded oocyte produced no current. Our results show that individual follicles may be electrophysiologically different, though their uniform differentiation during vitellogenesis does not reflect such heterogeneity.

Two actions of juvenile hormone on the follicle cells of Rhodnius prolixus Stål

1975 ◽  
Vol 53 (8) ◽  
pp. 1187-1188 ◽  
Author(s):  
Randa Abu-Hakima ◽  
K. G. Davey
Keyword(s):  
Juvenile Hormone ◽  
Developmental Stages ◽  
Normal Animal ◽  
Rhodnius Prolixus ◽  
Follicle Cells ◽  
Follicular Epithelium ◽  
Intercellular Spaces

The follicular epithelium of vitellogenic oocytes from allatectomized females of Rhodnius fails to develop large intercellular spaces when exposed to juvenile hormone (JH) in vitro. This suggests that in the normal animal, the follicle cells require JH at two developmental stages. Differentiation of the cells in the presence of JH represents one requirement, and only those cells which have undergone this initial priming are fully competent to exhibit the second response, the development of intercellular spaces.

Active Transport by the Cecropia Midgut

1968 ◽  
Vol 48 (1) ◽  
pp. 25-37
Author(s):  
J. A. HASKELL ◽  
W. R. HARVEY ◽  
R. M. CLARK
Keyword(s):  
Developmental Stages ◽  
Potassium Concentration ◽  
Electrical Potential ◽  
Fourth Instar ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Systematic Effect ◽  
Nernst Equation ◽  
Hydrogen Ion Concentration ◽  
Intermediate Value

1. The electrical potential across the isolated midgut of five developmental stages of the Cecropia silkworm was studied by changing the concentration of single cations in solutions bathing each side of the midgut. The stages included feeding fourth-instar insects, insects moulting from the fourth to the fifth instar, feeding fifth-instar insects, insects which had evacuated their midguts, and insects spinning cocoons. 2. Average values of the initial maximal potential exhibited by the midgut in solutions containing K, Mg, and Ca but no Na, for the stages mentioned above, were 68, 83, 90, 124, and 2 mV., respectively. 3. In all of the developmental stages studied except the ‘spinning larva’, reducing the potassium concentration from 32 to 2 mM/l. on the blood-side of the isolated gut lowers the potential, on the lumen-side of the gut raises the potential and on both sides gives an intermediate value. 4. When the potential prior to a decrease in concentration of potassium on the blood-side is over 100 mV., the Nernst slope approaches 59 mV. 5. A tenfold reduction in the concentration of magnesium or the addition of 32 mM/l. sodium to the solutions bathing the isolated gut has no systematic effect on the potential. 6. A tenfold drop in the concentration of calcium in the solutions causes changes in the potential in the opposite direction from those predicted by the Nernst equation. 7. The pH of the midgut contents rises from early fourth instar to late fifth instar. The hydrogen-ion concentration of the blood is about 1000 times more than that of midgut contents in fifth-instar insects. 8. Neither synthetic ecdysone, partially purified natural ecdysone nor juvenile hormone has an effect on the potential or current of the isolated midgut over periods as long as 30 min.

Ultrastructural analysis of Drosophila ovarian follicles differing in yolk polypeptide (yps) composition

Development ◽  
1993 ◽  
Vol 117 (1) ◽  
pp. 319-328
Author(s):  
F. Giorgi ◽  
P. Lucchesi ◽  
A. Morelli ◽  
M. Bownes
Keyword(s):  
Golgi Apparatus ◽  
Juvenile Hormone ◽  
Developmental Stages ◽  
Ovarian Follicles ◽  
Endocytic Pathway ◽  
Intermediate Cell ◽  
Wild Type ◽  
Vesicular Traffic

Drosophila ovarian follicles were examined ultrastructurally to study the vesicular traffic in the cortical ooplasm. The endocytic pathway leading to the production of yolk spheres was visualized following in vivo or in vitro exposure to peroxidase. The Golgi apparatus and the yolk spheres of wild-type ovarian follicles were preferentially labelled by fixation with osmium zinc iodide (OZI). Labelling of wild-type ovarian follicles was compared to that of several mutant follicles--L186/Basc, fs(2)A17 and ap4--which are defective in vitellogenesis. In these mutants, the Golgi apparatus and the vesicles nearby were either scantly labelled or not labelled at all. In oocytes from flies homozygous for the gene fs(1)1163, the Golgi apparatus was labelled as in the controls, but no yolk spheres appeared to be labelled with OZI at any of the developmental stages. In several Drosophila strains, the pattern of OZI label in the cortical ooplasm was seen to vary in relation to the number of yp structural genes. In starved Drosophila females, OZI labelling of the cortical ooplasm appeared restricted to the Golgi apparatus and to an extended tubular network. A similar labelling pattern was also detected in in vitro cultured vitellogenic follicles. Refeeding, topical application of juvenile hormone analogue to starved females or hormone addition to the culture medium, all caused the yolk spheres to become labelled with OZI and to incorporate peroxidase. These observations prove that impairing endocytic uptake by either mutation or lack of juvenile hormone prevents fusion of coated vesicles and tubules with the yolk spheres and leads them instead to form an intermediate cell compartment with Golgi-derived vesicles.

Blood Gas Analysis

2011 ◽  
Author(s):  
Patrick Magee ◽  
Mark Tooley
Keyword(s):  
Electrical Potential ◽  
Physical Principle ◽  
Gas Analysis ◽  
The Other ◽  
Potential Difference ◽  
Ion Concentration ◽  
Blood Gas ◽  
Glass Membrane ◽  
Current Flows ◽  
Ph Electrode

A blood gas machine has electrodes to measure pH, pCO2 and pO2 and often measures Hb and some biochemistry as well [King et al. 2000]. Derived values from such a device include O2 saturation, O2 content, bicarbonate, base excess and total CO2. This is the Clarke electrode described in the previous section on gas analysers and is suitable for both respiratory and blood O2 analysis. A pH unit has been defined in Chapter 1 as. In words, this can be described as ‘the negative logarithm, to base ten, of the hydrogen ion concentration’. The physical principle on which the pH electrode is based depends on the fact that when a membrane separates two solutions of different [H+], a potential difference exists across the membrane. In a pH electrode, such a membrane is usually made of glass and the development of a potential difference between the two solutions is thought to be due to the migration of H+ into the glass matrix. If one solution consists of a standard [H+], the pH of the other solution can be estimated by measurement of the potential difference between them. The glass membrane used is selectively permeable to H+. No current flows in this device, which does not wear out, in contrast to the Clark electrode, in which current does flow and that does need periodic replacement. The pH measurement system is shown diagrammatically in Figure 17.1. It consists of two half cells. In one half it has an Ag/AgCl electrode and in the other a Hg/HgCl2 (calomel) electrode. Each electrode maintains a fixed electrical potential. The Ag/AgCl electrode is surrounded by a buffer solution of known pH, surrounded by the pH sensitive glass. Outside the glass membrane is the test solution, usually blood, whose pH is to be measured. It is the potential difference across the glass, between these two solutions, which is variable. The blood or other solution is separated from the calomel electrode by a porous plug and a potassium chloride salt bridge to minimise KCl diffusion. The potential difference across the system is about 60 mV per unit of pH change at 37◦C.

scholarly journals Transmural electrical potential difference in the mammalian esophagus in vivo

1978 ◽  
Vol 75 (2) ◽  
pp. 286-291 ◽  
Author(s):  
Keith S. Turner ◽  
Don W. Powell ◽  
Charles N. Carney ◽  
Roy C. Orlando ◽  
Eugene M. Bozymski
Keyword(s):  
Electrical Potential ◽  
Potential Difference ◽  
Electrical Potential Difference
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