scholarly journals Basal lamina of ovarian follicle regulates an inward Cl− current in differentiated granulosa cells

2002 ◽  
Vol 282 (1) ◽  
pp. C34-C48 ◽  
Author(s):  
Wuxuan Qin ◽  
Stanley G. Rane ◽  
Elikplimi K. Asem
Keyword(s):  
Basement Membrane ◽  
Basal Lamina ◽  
Granulosa Cells ◽  
Ovarian Follicle ◽  
Outward Current ◽  
Delayed Rectifier ◽  
Membrane Area ◽  
Inward Current ◽  
Cells Cultured ◽  
In Cells

Patch-clamp experiments were conducted to study the effects of basal lamina (basement membrane) of preovulatory chicken ovarian follicle on membrane currents in differentiated chicken granulosa cells in a homologous system. The membrane capacitance (measure of total membrane area) was smaller in cells cultured on intact basal lamina than that of control cells. The granulosa cells expressed outward and two inward currents. A small fraction of the cells (3%) expressed only a transient fast-activating and -inactivating inward current carried by Ca2+. The majority of the cells, however, expressed a slowly activating and inactivating inward current (carried by Cl−) that was superimposed on the transient Ca2+ current. All cells expressed an outward current characteristic of the delayed-rectifier K+ current. The removal of extracellular Ca2+ led to elimination of the slow inward Cl− current, indicating that it is a Ca2+-dependent Cl− current. Both peak amplitude and current density of the inward Cl− current were significantly lower in cells cultured on freshly isolated intact basal lamina (or basal lamina stored at 4°C for 12 mo) than those of control cells; however, basal lamina had no significant effect on the density of the outward current. Similar to the observations made for intact basal lamina, solubilized basal lamina suppressed the inward Cl− current in differentiated granulosa cells. These data show that homologous basal lamina modulates a Ca2+-dependent Cl− current in differentiated granulosa cells. These findings provide a partial explanation for the mechanisms that subserve the reported effects of basal lamina (basement membrane) on the metabolic functions of differentiated granulosa cells.

Effect of basal lamina of ovarian follicle on T- and L-type Ca2+ currents in differentiated granulosa cells

2002 ◽  
Vol 282 (1) ◽  
pp. E184-E196 ◽  
Author(s):  
Elikplimi K. Asem ◽  
Wuxuan Qin ◽  
Stanley G. Rane
Keyword(s):  
Patch Clamp ◽  
Basal Lamina ◽  
Granulosa Cells ◽  
Ovarian Follicle ◽  
Matrix Material ◽  
Spherical Shape ◽  
Membrane Capacitance ◽  
Patch Clamp Technique ◽  
Indirect Measure ◽  
In Cells

Patch clamp experiments were conducted to study the effects of basal lamina (basement membrane) of chicken ovarian follicle on membrane Ca2+ currents in differentiated chicken granulosa cells in a homologous system. The whole cell patch clamp technique was used to simultaneously monitor membrane capacitance (an indirect measure of total cell surface area) and currents flowing through voltage-dependent Ca2+ channels (using Ba2+ as the charge carrier). Membrane capacitance was smaller in cells incubated on intact basal lamina than in control cells (incubated on tissue culture-treated plastic substratum). Granulosa cells expressed both T- and L-type Ca2+ currents, and the amplitudes of the currents in cells incubated on intact basal lamina were significantly lower than those of control cells. Also, granulosa cells incubated on intact basal lamina were found to have significantly lower T- or L-type Ca2+ current densities than control cells. Intact basal lamina that had been stored for 12 mo produced effects on T- and L-type Ca2+ currents similar to those caused by freshly isolated basal lamina. The basal lamina was solubilized completely in one step and used to coat glass coverslips (uncoated glass coverslips served as controls). Granulosa cells incubated on coverslips precoated with solubilized basal lamina assumed spherical shape similar to those incubated on intact basal lamina. Similar to the observations made for intact basal lamina, the solubilized basal lamina suppressed T- and L-type Ca2+ currents in the differentiated granulosa cells. Moreover, fibronectin, laminin, and type IV collagen, obtained from commercial sources, attenuated T- and L-type Ca2+ currents in the differentiated granulosa cells. This interplay between basal lamina and Ca2+ currents may be one mechanism that subserves the effects of the matrix material on metabolic functions of granulosa cells.

Yolk transport in the ovarian follicle of the hen (Gallus domesticus): lipoprotein-like particles at the periphery of the oocyte in the rapid growth phase

1979 ◽  
Vol 39 (1) ◽  
pp. 257-272 ◽  
Author(s):  
M.M. Perry ◽  
A.B. Gilbert
Keyword(s):  
Basal Lamina ◽  
Granulosa Cells ◽  
Plasma Membranes ◽  
Ovarian Follicle ◽  
Cell Loss ◽  
Coated Vesicles ◽  
Morphological Alteration ◽  
Tissue Preparation ◽  
Very Low Density Lipoproteins ◽  
Thin Sections

Thin sections of the oocyte periphery and surrounding granulosa layer from 1–5 day preovulatory follicles were examined by transmission electron microscopy. With the use of certain procedures in tissue preparation, notably the tannic acid method, numerous particles in the range of 15–40 nm with a mean diameter of 27 nm were observed in both extra- and intracellularly. The particles were abundant in the granulosa basal lamina, in the spaces between the granulosa cells and in the perivitelline space. They appeared to adhere to the oolemma as a continuous double layer which was also observed to line the coated vesicles, 200–350 nm in diameter, invaginating from the oolemma. The layer of particles was not found on the plasma membranes of the granulosa cells, nor were particles present within the cells. In the peripheral cytoplasm of the oocyte the yolk spheres, ranging upwards from 250 nm diameter, were membrane-bound and contained tightly packed particles similar to those on the oolemma. Bodies displaying features intermediate between coated vesicles and yolk spheres suggested that, on entry into the cell, loss of the cytoplasmic coat and obliteration of the vesicular lumen gave rise to nascent yolk spheres which then fused together to form the larger spheres. The extracellular layer, coated vesicles and smaller yolk spheres were absent in oocytes fixed after a 10-min delay. The evidence indicated that 27-nm particles were transferred from the basal lamina to the oocyte surface via the intergranulosa cell channels, incorporated into the cell by adsorptive endocytosis and then transferred to the yolk spheres with little morphological alteration. The identity of the particles with very low density lipoproteins, the major components of the yolk solids, was discussed.

Whole-cell patch-clamp analysis of voltage-dependent calcium conductances in cultured embryonic rat hippocampal neurons

1989 ◽  
Vol 61 (3) ◽  
pp. 467-477 ◽  
Author(s):  
D. E. Meyers ◽  
J. L. Barker
Keyword(s):  
Patch Clamp ◽  
Hippocampal Neurons ◽  
Calcium Currents ◽  
Tetraacetic Acid ◽  
Whole Cell ◽  
Inward Current ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent ◽  
Cells Cultured ◽  
In Cells

1. Voltage-dependent calcium currents in embryonic (E18) hippocampal neurons cultured for 1-14 days were investigated using the whole-cell patch-clamp technique. 2. Calcium currents were isolated by removing K+ from both the internal and external solutions. In most recordings the external solution contained tetrodotoxin, tetraethylammonium ions, and low concentrations of Na+, whereas the internal solution contained the large cations and anions, N-methyl-D-glucamine and methanesulphonate, and an adenosine 5'-triphosphate (ATP) regenerating system (Forscher and Oxford, 1985) to retard “run-down” of Ca currents. 3. Under these conditions, the sustained inward current triggered during depolarizing steps was enhanced when extracellular [Ca2+] ([Ca2+]0) was raised from 2 to 10 mM and abolished when [Ca2+]0 was lowered to 0.1 mM or by addition of Co2+ ions. These results indicate that the inward current was carried primarily by Ca2+ ions and was designated ICa. This current may be comparable to the “high-voltage-activated” Ca current described in other preparations. 4. In cells cultured for 1-3 days, ICa was small or absent (less than 20 pA for cells 1 day in culture and less than 80 pA for cells 3 days in culture). Although ICa decayed considerably during depolarizing steps, there was little evidence of the transient calcium current (T current) that was recorded in approximately 40% of cells cultured longer than 6 days. Maximal (i.e., the largest) ICa increased from 20 to 80 pA in 1- to 3-day cells to 150–450 pA in cells cultured for longer than 6 days. 5. The decay of ICa elicited by depolarizations from holding potentials of -60 mV or more negative was usually greatest for the maximal ICa. Replacement of extracellular Ca2+ (4 mM) with Ba2+ (2 mM) resulted in a substantial decrease in the extent of decay of ICa and a shift of the I-V relation in the hyperpolarizing direction. 6. Qualitative data obtained from experiments in which different levels of internal Ca2+ buffering were employed demonstrated that, on average, the decay of ICa was reduced as the capacity and/or rate of buffering was increased. The mean decay of ICa in cells buffered with 5 mM 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) was 9 +/- 7 (SD) %, (n = 12) and 25 +/- 12%, (n = 12) for cells buffered with the same concentration of ethyleneglycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA).(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Voltage-dependent conductances in Limulus ventral photoreceptors.

1982 ◽  
Vol 79 (2) ◽  
pp. 187-209 ◽  
Author(s):  
J E Lisman ◽  
G L Fain ◽  
P M O'Day
Keyword(s):  
Outward Current ◽  
Delayed Rectifier ◽  
Molluscan Neurons ◽  
Inward Current ◽  
Transient Component ◽  
Outward Currents ◽  
Voltage Dependent ◽  
Inward Currents ◽  
K Current ◽  
A Current

The voltage-dependent conductances of Limulus ventral photoreceptors have been investigated using a voltage-clamp technique. Depolarization in the dark induces inward and outward currents. The inward current is reduced by removing Na+ or Ca2+ and is abolished by removing both ions. These results suggest that both Na+ and Ca2+ carry voltage-dependent inward current. Inward current is insensitive to tetrodotoxin but is blocked by external Ni2+. The outward current has a large transient component that is followed by a smaller maintained component. Intracellular tetraethylammonium preferentially reduces the maintained component, and extracellular 4-amino pyridine preferentially reduces the transient component. Neither component is strongly affected by removal of extracellular Ca2+ or by intracellular injection of EGTA. It is concluded that the photoreceptors contain at least three separate voltage-dependent conductances: 1) a conductance giving rise to inward currents; 2) a delayed rectifier giving rise to maintained outward K+ current; and 3) a rapidly inactivating K+ conductance similar to the A current of molluscan neurons.

scholarly journals Calcium currents in a fast-twitch skeletal muscle of the rat.

1983 ◽  
Vol 82 (4) ◽  
pp. 449-468 ◽  
Author(s):  
P L Donaldson ◽  
K G Beam
Keyword(s):  
Skeletal Muscle ◽  
Leakage Current ◽  
Calcium Current ◽  
Outward Current ◽  
Extracellular Calcium ◽  
Calcium Currents ◽  
Slow Inward Current ◽  
Delayed Rectifier ◽  
Inward Current ◽  
Time To Peak

Slow ionic currents were measured in the rat omohyoid muscle with the three-microelectrode voltage-clamp technique. Sodium and delayed rectifier potassium currents were blocked pharmacologically. Under these conditions, depolarizing test pulses elicited an early outward current, followed by a transient slow inward current, followed in turn by a late outward current. The early outward current appeared to be a residual delayed rectifier current. The slow inward current was identified as a calcium current on the basis that (a) its magnitude depended on extracellular calcium concentration, (b) it was blocked by the addition of the divalent cations cadmium or nickel, and reduced in magnitude by the addition of manganese or cobalt, and (c) barium was able to replace calcium as an inward current carrier. The threshold potential for inward calcium current was around -20 mV in 10mM extracellular calcium and about -35 mV in 2 mM calcium. Currents were net inward over part of their time course for potentials up to at least +30 mV. At temperatures of 20-26 degrees C, the peak inward current (at approximately 0 mV) was 139 +/- 14 microA/cm2 (mean +/- SD), increasing to 226 +/- 28 microA/cm2 at temperatures of 27-37 degrees C. The late outward current exhibited considerable fiber-to-fiber variability. In some fibers it was primarily a time-independent, nonlinear leakage current. In other fibers it was primarily a time-independent, nonlinear leakage current. In other fibers it appeared to be the sum of both leak and a slowly activated outward current. The rate of activation of inward calcium current was strongly temperature dependent. For example, in a representative fiber, the time-to-peak inward current for a +10-mV test pulse decreased from approximately 250 ms at 20 degrees C to 100 ms at 30 degrees C. At 37 degrees C, the time-to-peak current was typically approximately 25 ms. The earliest phase of activation was difficult to quantify because the ionic current was partially obscured by nonlinear charge movement. Nonetheless, at physiological temperatures, the rate of calcium channel activation in rat skeletal muscle is about five times faster than activation of calcium channels in frog muscle. This pathway may be an important source of calcium entry in mammalian muscle.

scholarly journals Whole-cell clamp of dissociated photoreceptors from the eye of Lima scabra.

1991 ◽  
Vol 97 (1) ◽  
pp. 35-54 ◽  
Author(s):  
E Nasi
Keyword(s):  
Calcium Influx ◽  
Large Fraction ◽  
Outward Current ◽  
Light Response ◽  
Stimulus Onset ◽  
Delayed Rectifier ◽  
Transient Outward Current ◽  
Whole Cell ◽  
Inward Current ◽  
Voltage Dependent

Voltage-dependent membrane currents were investigated in enzymatically dissociated photoreceptors of Lima scabra using the whole-cell clamp technique. Depolarizing steps to voltages more positive than -10 mV elicit a transient inward current followed by a delayed, sustained outward current. The outward current is insensitive to replacement of a large fraction of extracellular Cl- with the impermeant anion glucuronate. Superfusion with tetraethylammonium and 4-aminopyridine reversibly abolishes the outward current, and internal perfusion with cesium also suppresses it, indicating that it is mediated by potassium channels. Isolation of the inward current reveals a fast activation kinetics, the peak amplitude occurring as early as 4-5 ms after stimulus onset, and a relatively rapid, though incomplete inactivation. Within the range of voltages examined, spanning up to +90 mV, reversal was not observed. The inward current is not sensitive to tetrodotoxin at concentrations up to 10 microM, and survives replacement of extracellular Na with tetramethylammonium. On the other hand, it is completely eliminated by calcium removal from the perfusing solution, and it is partially blocked by submillimolar concentrations of cadmium, suggesting that it is entirely due to voltage-dependent calcium channels. Analysis of the kinetics and voltage dependence of the isolated calcium current indicates the presence of two components, possibly reflecting the existence of separate populations of channels. Barium and strontium can pass through these channels, though less easily than calcium. Both the activation and the inactivation become significantly more sluggish when these ions serve as the charge carrier. A large fraction of the outward current is activated by preceding calcium influx. Suppression of this calcium-dependent potassium current shows a small residual component resembling the delayed rectifier. In addition, a transient outward current sensitive to 4-aminopyridine (Ia) could also be identified. The relevance of such conductance mechanisms in the generation of the light response in Lima photoreceptors is discussed.

Whole-cell recording of light-evoked photoreceptor responses in a slice preparation of the cuttlefish retina

2005 ◽  
Vol 22 (3) ◽  
pp. 359-370 ◽  
Author(s):  
ABDESSLAM CHRACHRI ◽  
LISA NELSON ◽  
RODDY WILLIAMSON
Keyword(s):  
Time Course ◽  
Early Stage ◽  
Outward Current ◽  
Delayed Rectifier ◽  
Dependent Manner ◽  
Slice Preparation ◽  
Whole Cell ◽  
Inward Current ◽  
Transient Inward Current ◽  
Dose Dependent

A new tissue slice preparation of the cuttlefish eye is described that permits patch-clamp recordings to be acquired from intact photoreceptors during stimulation of the retina with controlled light flashes. Whole-cell recordings using this preparation, from the retinas of very youngSepia officinalisdemonstrated that the magnitude, latency, and kinetics of the flash-induced photocurrent are closely dependent on the magnitude of the flash intensity. Depolarizing steps to voltages more positive than −40 mV, from a membrane holding potential of −60 mV, induced a transient inward current followed by a larger, more sustained outward current in these early-stage photoreceptors. The latter current resembled the delayed rectifier (IK) already identified in many other nerve cells, including photoreceptors. This current was activated at −30 mV from a holding potential of −60 mV, had a sustained time course, and was blocked in a dose-dependent manner by tetraethylammonium chloride (TEA). The smaller, transient, inward current appeared at potentials more positive than −50 mV, reached peak amplitude at −30 mV and decreased with further depolarization. This current was characterized as the sodium current (INa) on the basis that it was inactivated at holding potentials above −40 mV, was blocked by tetrodotoxin (TTX) and was insensitive to cobalt.Intracellular perfusion of the photoreceptors,viathe patch pipette, demonstrated that U-73122 and heparin blocked the evoked photocurrent in a dose-dependent manner, suggesting the involvement of the phospholipase C (PLC) and inositol 1,4,5-triphosphate (InsP3), respectively, in the phototransduction cascade. Perfusion with cyclic GMP increased significantly the evoked photocurrent, while the inclusion of phorbol-12,13-dibutyrate reduced significantly the evoked photocurrent, supporting the involvement of cGMP and the diacylglycerol (DAG) pathways, respectively, in the cuttlefish transduction process.

Basal lamina of avian ovarian follicle: influence on morphology of granulosa cells in-vitro

2000 ◽  
Vol 125 (2) ◽  
pp. 189-201 ◽  
Author(s):  
Elikplimi K Asem ◽  
Shulin Feng ◽  
Susan R Stingley-Salazar ◽  
John J Turek ◽  
Augustine T Peter ◽  
...  
Keyword(s):  
Basal Lamina ◽  
Granulosa Cells ◽  
Ovarian Follicle

Low extracellular Ca2+ activates a transient Cl− current in chicken ovarian granulosa cells

2000 ◽  
Vol 279 (2) ◽  
pp. C319-C325 ◽  
Author(s):  
Wuxuan Qin ◽  
Stanley G. Rane ◽  
Elikplimi K. Asem
Keyword(s):  
Benzoic Acid ◽  
Granulosa Cells ◽  
Channel Blocker ◽  
Outward Current ◽  
Transient Outward Current ◽  
Ion Currents ◽  
Ovarian Granulosa Cells ◽  
Metabolic Functions ◽  
In Cells

The effects of low Ca2+ on ion currents in hen ovarian granulosa cells were examined. A fast activating and inactivating transient outward current (TOC) and a slowly activating outward current (SOC) could be observed. In the presence of normal Ca2+concentration (2.5 mM) and with a holding potential of −80 mV, SOC was activated in all cells with command pulses more positive than −20 mV. In 2.5 mM Ca2+, TOC appeared in 10% of cells at the command pulse of +80 mV and in 60–85% of cells at +100 to +120 mV. In low-Ca2+ solution and command potential of +80 mV (holding potential of −80 mV), the amplitude of TOC was enhanced in cells that expressed it in normal Ca2+, and TOC appeared in 43% of the cells that did not express it initially in normal Ca2+. At both normal and low Ca2+ levels, TOC decreased as the holding potential became more positive. TOC was reduced in Cl−-deficient solution and in the presence of 5-nitro-2-(3-phenylpropylamino)benzoic acid, a Cl− channel blocker. These findings suggest that chicken granulosa cells express a Ca2+-inactivated TOC carried by Cl−. This current may serve as a signal for some of the reduced metabolic functions of granulosa cells associated with Ca2+deficiency.

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