scholarly journals Secretory Potential and Ionic Transport in the Posterior Silk Glands of Bombyx Mori

1988 ◽  
Vol 134 (1) ◽  
pp. 155-171
Author(s):  
I. NAKAGAKI ◽  
S. SASAKI
Keyword(s):  
Membrane Potential ◽  
Basolateral Membrane ◽  
Extracellular Fluid ◽  
Silk Gland ◽  
X Ray ◽  
Gland Cells ◽  
Luminal Membrane ◽  
High K ◽  
Posterior Silk Gland ◽  
Basolateral Membrane Potential

The concentrations of Na, Mg, P, S, Cl, K and Ca in the cytoplasm and lumen of the posterior silk gland cells of Bombyx mori were measured by X-ray microprobe analysis of freeze-dried thin sections. The basal and luminal membrane potentials of the gland cells were measured using microelectrode techniques. The input resistance of the luminal plasma membrane was simultaneously measured by injecting electric current via an intracellular microelectrode. The basolateral membrane potential was −47 ± 1.8mV (S.E.) (N = 46), and the glands exhibited lumen-negative voltages of −6 ± 0.1 mV (S.E.) (N = 40) in the normal state. Increasing the extracellular K+ concentration depolarized the basolateral membrane potential, whereas the membrane potential hyperpolarized when Cl− concentration in the extracellular fluid was increased. There were no significant effects on the membrane potential when NaK+, MgK2+ and CaK2+ concentrations in the extracellular fluid were changed. The representative X-ray spectra showed high K and phosphorus peaks, and low Cl and Mg peaks in the cytoplasm of the normal posterior silk gland cells. The normal glandular lumen showed relatively high K, and low Cl, sulphur, Ca and Mg peaks. Quantitative microprobe values were, for the cytoplasm (mmol kg−1 wet mass, N = 30) Na, 5; Mg, 14; phosphorus, 168; sulphur, 16; Cl, 12; K, 168; Ca, 0.5; and for the lumen (N = 10) Na, 3; Mg, 25; phosphorus, 42; sulphur, 24; Cl, 38; K, 133; Ca, 9.4 in the normal glands. The basal plasma membrane potential was hyperpolarized by 7 mV after stimulation with 5×10−5 mmol l−1 5-hydroxytryptamine (5-HT). Microprobe values for the cytoplasm were (mmol kg−1 wet mass, N = 15) Na, 4; Mg, 13; phosphorus, 160; sulphur, 17; Cl, 8; K, 187; Ca, 0.6 in the stimulated glands. The cytoplasmic [K] increased after stimulation with 5-HT. The basal membrane potential of the gland cells was depolarized by 3 mV after application of a juvenoid, methoprene (10−5 mol l−1). X-ray microprobe values for the cytoplasm were (mmol kg−1 wet mass, N = 15) Na, 7; Mg, 11; P, 170; S, 14; Cl, 23; K, 130; Ca, 3.4 in the treated glands. The cytoplasmic [Ca] and [Cl] increased, while the [K] decreased with methoprene stimulation. The luminal membrane potential of the gland cells was depolarized by 8mV and a simultaneous decrease of luminal membrane resistance was apparent after stimulation with an anti-microfilament reagent, cytochalasin D (2×10−6mol l−1). X-ray microprobe values for the cytoplasm became (mmol kg−1 wet mass, N = 15) Na, 10; Mg, 28; P, 194; S, 22; Cl, 24; K, 148; Ca, 1.2; and for the lumen (N = 15) Na, 14; Mg, 13; phosphorus, 31; sulphur, 30; Cl, 92; K, 122; Ca, 1.1 in the stimulated glands. The cytoplasmic [Ca] and [Cl] increased and [K] decreased, whereas the luminal [Cl] and [sulphur] increased and [Ca] and [Mg] decreased after cytochalasin D stimulation. The reaction products of adenosine triphosphatase activity were found on the luminal and lateral plasma membranes of the posterior silk gland cells. The possible routes of ion transport into the lumen are discussed.

Effect of norepinephrine on intracellular pH in kidney proximal tubule: role of Na+-( HCO 3 − ) n cotransport

1998 ◽  
Vol 275 (1) ◽  
pp. F33-F45 ◽  
Author(s):  
Solange Abdulnour-Nakhoul ◽  
Raja N. Khuri ◽  
Nazih L. Nakhoul
Keyword(s):  
Membrane Potential ◽  
Proximal Tubule ◽  
Intracellular Ph ◽  
Basolateral Membrane ◽  
Inhibitory Effect ◽  
Rate Of Change ◽  
Kidney Proximal Tubule ◽  
Luminal Membrane ◽  
Basolateral Membrane Potential

We examined the effect of norepinephrine (NE) on intracellular pH (pHi) and activity of Na+([Formula: see text]) in the isolated perfused kidney proximal tubule of Ambystoma, using single-barreled voltage and ion-selective microelectrodes. In control[Formula: see text] Ringer, addition of 10−6 M NE to the bath reversibly depolarized the basolateral membrane potential ( V 1), the luminal membrane potential ( V 2), and the transepithelial potential difference ( V 3) and increased pHi by 0.14 ± 0.02. These effects were mimicked by isoproterenol but were abolished after pretreatment with SITS or in the absence of CO2/[Formula: see text]. Removal of bath Na+ depolarized V 1 and V 2, hyperpolarized V 3, and decreased pHi. These effects are largely mediated by the electrogenic Na+-([Formula: see text]) n cotransporter. In the presence of NE, the effects of Na+ removal on membrane potential differences and the rate of change of pHi were significantly smaller. Reducing bath [Formula: see text] concentration from 10 to 2 mM at constant CO2 (pH 6.8) depolarized V 1 and V 2, decreased pHi, and lowered[Formula: see text]. These changes are also due to Na+-([Formula: see text]) n . In the presence of NE, reducing bath [[Formula: see text]] caused a smaller depolarizations of V 1 and V 2, and the rate of pHi decrease was significantly reduced. Our results indicate: 1) NE causes an increase in pHi; 2) the NE-induced alkalinization is mediated by a SITS-sensitive and[Formula: see text]-dependent transporter on the basolateral membrane; and 3) in the presence of NE, the reduced effects caused by basolateral[Formula: see text] changes or Na+ removal are indicative of an inhibitory effect of NE on Na+-([Formula: see text]) n cotransport.

scholarly journals Enhanced Myc Expression in Silkworm Silk Gland Promotes DNA Replication and Silk Production

Insects ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 361
Author(s):  
Wenliang Qian ◽  
Yan Yang ◽  
Zheng Li ◽  
Yuting Wu ◽  
Xuechuan He ◽  
...  
Keyword(s):  
Dna Replication ◽  
Cell Growth ◽  
Silk Gland ◽  
Biological Functions ◽  
Gland Cells ◽  
Silk Production ◽  
Myc Gene ◽  
Cell Growth And Proliferation ◽  
Silkworm Silk ◽  
Posterior Silk Gland

Silkworm is an economically important insect that synthetizes silk proteins for silk production in silk gland, and silk gland cells undergo endoreplication during larval period. Transcription factor Myc is essential for cell growth and proliferation. Although silkworm Myc gene has been identified previously, its biological functions in silkworm silk gland are still largely unknown. In this study, we examined whether enhanced Myc expression in silk gland could facilitate cell growth and silk production. Based on a transgenic approach, Myc was driven by the promoter of the fibroin heavy chain (FibH) gene to be successfully overexpressed in posterior silk gland. Enhanced Myc expression in the PSG elevated FibH expression by about 20% compared to the control, and also increased the weight and shell rate of the cocoon shell. Further investigation confirmed that Myc overexpression increased nucleus size and DNA content of the PSG cells by promoting the transcription of the genes involved in DNA replication. Therefore, we conclude that enhanced Myc expression promotes DNA replication and silk protein expression in endoreplicating silk gland cells, which subsequently raises silk yield.

scholarly journals EXTRUSION OF NUCLEAR MATERIALS INTO CYTOPLASM IN THE POSTERIOR SILK GLAND CELLS OF SILKWORM, BOMBYX MORI

1968 ◽  
Vol 36 (3) ◽  
pp. C5-10 ◽  
Author(s):  
Yutaka Tashiro ◽  
Shiro Matsuura ◽  
Takashi Morimoto ◽  
Sunao Nagata
Keyword(s):  
Bombyx Mori ◽  
Silk Gland ◽  
Nuclear Materials ◽  
Gland Cells ◽  
Silkworm Bombyx Mori ◽  
Posterior Silk Gland

scholarly journals Lysosomes and Related Structures in the Posterior Silk Gland Cells ofBombyx mori. I. In Late Larval Stadium

1976 ◽  
Vol 1 (3) ◽  
pp. 205-222 ◽  
Author(s):  
Yutaka Tashiro ◽  
Takeo Shimadzu ◽  
Shiro Matsuura
Keyword(s):  
Silk Gland ◽  
Gland Cells ◽  
Posterior Silk Gland

Relation of membrane potential to basolateral TEA transport in isolated snake proximal renal tubules

1995 ◽  
Vol 268 (6) ◽  
pp. R1539-R1545 ◽  
Author(s):  
Y. K. Kim ◽  
W. H. Dantzler
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Potent Inhibitor ◽  
Basolateral Membrane ◽  
Potential Difference ◽  
Renal Tubules ◽  
K Concentration ◽  
Electrochemical Equilibrium ◽  
Membrane Potential Difference ◽  
Basolateral Membrane Potential

We measured the effects of changes in bath K+ concentration ([K+]) on basolateral membrane potential difference (PD) and [3H]tetraethylammonium (TEA) transport in isolated snake (Thamnophis) proximal renal tubules (25 degrees C; pH 7.4). Increasing bath [K+] from 3 to 65 mM decreased PD from -60 mV (inside of cells negative) to -20 mV and 2-min uptake of [3H]TEA by approximately 25%, indicating that PD influences TEA entry into the cells. Uptake of [3H]TEA was inhibited similarly at both K+ concentrations by unlabeled TEA, indicating that uptake is carrier mediated. Kt (approximately 18 microM) for 2-min uptake of [3H]TEA in 3 mM K+ increased significantly in 65 mM K+, suggesting that the decrease in PD or the increase in [K+] alters the affinity of the transporter for TEA. The steady-state cell-to-bath ratio for [3H]TEA with 3 mM K+ (-60 mV PD) was approximately 16, significantly above the ratio of 10 predicted for passive distribution at electrochemical equilibrium. With 65 mM K+ (-20 mV PD) this ratio decreased to approximately 6, again significantly above the predicted ratio of 2. These data suggest that the PD can account for much, but not all, of the steady-state uptake of TEA. Efflux of [3H]TEA across the basolateral membrane was identical with either 3 or 65 mM K+ in the bath but was almost completely inhibited in either case by tetrapentylammonium, a potent inhibitor of TEA uptake. These data indicate that virtually all TEA transport across the basolateral membrane is carrier mediated and that transport out of the cells is unaffected by PD.

Intracellular potentials in rabbit proximal tubules perfused in vitro

1981 ◽  
Vol 240 (3) ◽  
pp. F200-F210 ◽  
Author(s):  
B. Biagi ◽  
T. Kubota ◽  
M. Sohtell ◽  
G. Giebisch
Keyword(s):  
Membrane Potential ◽  
Basolateral Membrane ◽  
Proximal Tubules ◽  
Rabbit Kidney ◽  
Electrical Measurements ◽  
Proximal Tubular ◽  
The Mean ◽  
Number Of Cells ◽  
Basolateral Membrane Potential

Conventional microelectrodes were used to measure the basolateral membrane potential (VBL) in isolated perfused superficial proximal convoluted (sPCT) and superficial proximal straight (sPST) tubules of the rabbit kidney. Stable recordings for periods up to 2 h can be obtained. The mean +/- SE (n = number of cells) values of VBL were sPCT = -51.0 +/- 1.63 (24) and sPST = -47.0 +/- 0.97 (94) mV. Inhibitors of active transport, ouabain (10(-5) M) and low bath potassium (0.1 mM), caused a significant depolarization of VBL in sPST. In contrast, short-duration bath cooling (10 degrees C) had no significant effect. Removal of luminal glucose caused a larger hyperpolarization in sPCT (-13.9 +/- 1.77 (9) mV) than in sPST (-3.8 +/- 1.02 (5) mV). Removal of luminal glucose and alanine resulted in an even larger hyperpolarization of VBL in sPCT (-19.0 +/- 0.44 (6) mV). Perfusion of the lumen with a solution resembling late proximal tubular fluid in sPST resulted in hyperpolarization of VBL (-4.3 +/- 0.85 (4) mV). Reducing bath pH to 6.7 depolarized VBL (39.9 +/- 1.77 (13) mV). This effect can be associated with a decrease in the relative potassium permeability of the basolateral membrane. These results demonstrate the feasibility of using intracellular electrical measurements to determine both luminal and basolateral membrane characteristics in isolated proximal tubular segments.

Direct measurement of basolateral membrane potentials from cells of the macula densa

1989 ◽  
Vol 257 (3) ◽  
pp. F463-F468 ◽  
Author(s):  
P. D. Bell ◽  
J. Y. Lapointe ◽  
J. Cardinal
Keyword(s):  
Membrane Potential ◽  
Direct Measurement ◽  
Basolateral Membrane ◽  
Membrane Potentials ◽  
Macula Densa ◽  
Rabbit Kidney ◽  
Fluid Composition ◽  
Nacl Solution ◽  
Basolateral Membrane Potential

At the present time, little is known concerning the electrophysiology of the cells of the macula densa and whether or not these cells are electrically responsive to alterations in luminal fluid composition. To investigate this issue, cortical thick ascending limbs (CTAL) containing macula densa and attached glomeruli were dissected from rabbit kidney and the CTAL perfused in vitro. Basolateral membrane potential (Vbl) was measured with microelectrodes in macula densa cells and, for comparison, in cells of the CTAL. Macula densa Vbl averaged -56.5 +/- 7.6 mV (n = 4) at a (n = 22) at 20 mM NaCl, -35.6 +/- 3.9 mV (n = 16) at 45 mM NaCl, and -25.5 +/- 2.6 mV (n = 32) at 150 mm NaCl. Thus macula densa Vbl depolarized markedly (31 mV) when luminal perfusate [NaCl] was increased from low to high values. In contrast, Vbl measured in CTAL cells averaged -62 +/- 6.1 mV (n = 6) in 45 mM NaCl and did not change significantly as perfusate NaCl was increased to 150 mM. In the presence of 150 mM NaCl, luminal application of furosemide (50 microM) produced a small (3.5 +/- 1.1 mV, n = 16) but statistically significant (P less than 0.02) hyperpolarization in macula densa cells, whereas CTAL cell Vbl hyperpolarized markedly (20 +/- 5.7 mV, n = 6) with addition of furosemide. Finally, neither macula densa cells nor the CTAL cells changed Vbl when 45 mM NaCl solution was made hypotonic by removing mannitol.(ABSTRACT TRUNCATED AT 250 WORDS)

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