scholarly journals Characterization of the calcium-sequestering process associated with human platelet intracellular membranes isolated by free-flow electrophoresis

1984 ◽  
Vol 222 (2) ◽  
pp. 413-417 ◽  
Author(s):  
S Menashi ◽  
K S Authi ◽  
F Carey ◽  
N Crawford
Keyword(s):  
Steady State ◽  
Human Platelet ◽  
State Level ◽  
Free Flow ◽  
Ionophore A23187 ◽  
Steady State Level ◽  
Uptake Process ◽  
Steady State Levels ◽  
Gradient Fractionation

By using density-gradient fractionation and high-voltage free-flow electrophoresis, human platelet membranes were separated into highly purified subfractions of surface (SM) and intracellular (IM) origin. Associated exclusively with the IM fraction is an ATP-dependent Ca2+ uptake that, in the absence of oxalate, reaches steady-state levels in 5-10 min. When Ca2+-EGTA buffers were used to control the external Ca2+ concentrations (range 0.1-50 microM) there was an increase in the intravesicle steady-state level of Ca2+ up to 10 microM external Ca2+ concentration. Above this level the intravesicle space becomes saturated at a concentration between 10 and 20 nmol of Ca2+ X (mg of protein)-1. The ionophore A23187 promotes a rapid and almost total release of the sequestered Ca2+ (greater than 90%, t1/2 1-2 min). The presence of oxalate in the external medium greatly enhances the Ca2+ accumulation to levels as high as 200 nmol X (mg of protein)-1, but the uptake process is more variable and rarely reaches steady-state level even after 2 h incubation. Moreover, accumulation in the presence of oxalate effects ionophore release with less than 80% depletion in 45-60 min. These findings, taken together with the known presence in the platelet of a wide variety of functional and metabolic processes triggered by this cation, suggest that the platelet IM has a key role in controlling cytosolic Ca2+ concentrations.

scholarly journals Characterization of the Bradyrhizobium japonicum ftsH Gene and Its Product

1999 ◽  
Vol 181 (23) ◽  
pp. 7394-7397 ◽  
Author(s):  
Franz Narberhaus ◽  
Carmen Urech ◽  
Hauke Hennecke
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Western Blot ◽  
Bradyrhizobium Japonicum ◽  
State Level ◽  
Growth Conditions ◽  
Cellular Function ◽  
Steady State Level

ABSTRACT The Bradyrhizobium japonicum ftsH gene was cloned by using a set of widely applicable degenerated oligonucleotides. Western blot experiments indicated that the FtsH protein was produced under standard growth conditions and that it was not heat inducible. Attempts to delete the ftsH gene in B. japonicum failed, suggesting a pivotal cellular function of this gene. The expression ofB. japonicum ftsH in an ftsH-negativeEscherichia coli strain significantly enhanced the fitness of this mutant and reduced the steady-state level of ς32.

Induction of gene expression during involution of the lactating mammary gland of the rat

1994 ◽  
Vol 12 (1) ◽  
pp. 47-60 ◽  
Author(s):  
R S Guenette ◽  
H B Corbeil ◽  
J Léger ◽  
K Wong ◽  
V Mézl ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mammary Gland ◽  
Steady State ◽  
Epithelial Cells ◽  
Tissue Transglutaminase ◽  
State Level ◽  
Ultrastructural Changes ◽  
Steady State Level ◽  
Hsp 27 ◽  
Steady State Levels

ABSTRACT After weaning, the mammary gland ceases lactation and involutes. The wet weight of the gland decreases by 70% within 4 days of weaning. This involves significant tissue remodelling as the ducts regress and return to the resting state. The presence of apoptotic bodies in the luminal epithelial compartment 2 to 3 days after weaning provides clear evidence that a substantial proportion of the regression is attributable to the induction of active cell death (ACD) of the epithelial cells. These changes in the architecture of the gland were found to be mirrored by changes in gene expression. The steady-state level of β-casein mRNA decreased rapidly after weaning from the high levels seen during lactation to undetectable levels by 8 days after weaning. The steady-state levels of expression of a number of genes associated with ACD, including TRPM-2, tissue transglutaminase (TGase) and poly(ADP-ribose) polymerase (PARP), increased transiently during this time-frame. The steady-state level of TRPM-2 mRNA increased 2 days after weaning, reaching a peak on day 4, and decreasing to undetectable levels by day 8 after weaning. The steady-state levels of two other mRNAs, TGase and PARP, showed very similar kinetics. In contrast, the mRNA for Hsp 27, which has been shown to be induced during prostate regression, was not significantly induced in the regressing mammary gland. In-situ hybridization demonstrated that the TRPM-2, TGase and PARP genes were expressed predominantly in the luminal epithelial cells of the ducts. These cells expressed β-casein mRNA during lactation, and underwent ACD after weaning. While the ultrastructural changes in the mammary gland after weaning, and the induction of TRPM-2, TGase and PARP mRNAs, are reminiscent of apoptosis in the prostate, several features of the process are different. Most notably, the disruption of the secretory processes and the lack of increased expression of Hsp 27 in the regressing mammary gland suggest that there may be a number of important events in ACD that are not common to all cells.

Effect of ANP on sustained aldosterone secretion stimulated by angiotensin II

1989 ◽  
Vol 256 (1) ◽  
pp. C89-C95 ◽  
Author(s):  
C. M. Isales ◽  
W. B. Bollag ◽  
L. C. Kiernan ◽  
P. Q. Barrett
Keyword(s):  
Steady State ◽  
Angiotensin Ii ◽  
Protein Phosphorylation ◽  
State Level ◽  
Secretory Response ◽  
Ionophore A23187 ◽  
Steady State Level ◽  
Ang Ii ◽  
Aldosterone Secretion ◽  
Influx Rate

The sustained aldosterone secretory response to angiotensin II (ANG II) depends on receptor-mediated increases in membrane diglyceride (DG) and an increase in calcium influx rate. These signals serve to activate membrane-associated protein kinase C (PKC) and result in enhanced phosphorylation of a unique set of proteins. These events can be mimicked by the addition of a phorbol ester, 12-O-tetra decanoyl phorbol 13-acetate (TPA), and a calcium ionophore, A23187, that bypass the initial receptor-associated events. We studied the inhibitory action of atrial natriuretic peptide (4-28 hANP) on the sustained secretory response to ANG II in isolated bovine adrenal glomerulosa cells. Although 10 nM ANP inhibited aldosterone secretion, it did not significantly alter the ANG II-elicited rise in 45Ca2+ influx rate [control (CON): 0.44 +/- 0.06; ANG II: 1.11 +/- 0.12 (P less than 0.001); ANG II + ANP: 1.18 +/- 0.14], the steady-state level of aequorin luminescence [intracellular [Ca2+] ([Ca2+]i)], or the rise in cellular DG content [CON: 0.132 +/- 0.01; ANG II: 0.194 +/- 0.01 (P less than 0.005); ANG II + ANP: 0.202 +/- 0.01 nmol/10(6) cells]. IN addition, ANP was able to inhibit aldosterone secretion stimulated by the combined addition of A23187 + TPA. When protein phosphorylation in the ANP-inhibited cells was evaluated, ANG II-induced protein phosphorylation events were preserved. In contrast to the effect of ANP, the calcium channel blocker nitrendipine abolished the ANG II-induced rise in 45Ca2+ influx rate, reduced the steady-state level of [Ca2+]i, and returned the phosphoproteins to their control states.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals The COG complex interacts directly with Syntaxin 6 and positively regulates endosome-to-TGN retrograde transport

2011 ◽  
Vol 194 (3) ◽  
pp. 459-472 ◽  
Author(s):  
Orly Laufman ◽  
WanJin Hong ◽  
Sima Lev
Keyword(s):  
Steady State ◽  
State Level ◽  
Retrograde Transport ◽  
Snare Complex ◽  
Steady State Level ◽  
Cog Complex ◽  
Target Membrane ◽  
Steady State Levels ◽  
Retrograde Traffic ◽  
Golgi Network

The conserved oligomeric Golgi (COG) complex has been implicated in the regulation of endosome to trans-Golgi network (TGN) retrograde trafficking in both yeast and mammals. However, the exact mechanisms by which it regulates this transport route remain largely unknown. In this paper, we show that COG interacts directly with the target membrane SNARE (t-SNARE) Syntaxin 6 via the Cog6 subunit. In Cog6-depleted cells, the steady-state level of Syntaxin 6 was markedly reduced, and concomitantly, endosome-to-TGN retrograde traffic was significantly attenuated. Cog6 knockdown also affected the steady-state levels and/or subcellular distributions of Syntaxin 16, Vti1a, and VAMP4 and impaired the assembly of the Syntaxin 6–Syntaxin16–Vti1a–VAMP4 SNARE complex. Remarkably, overexpression of VAMP4, but not of Syntaxin 6, bypassed the requirement for COG and restored endosome-to-TGN trafficking in Cog6-depleted cells. These results suggest that COG directly interacts with specific t-SNAREs and positively regulates SNARE complex assembly, thereby affecting their associated trafficking steps.

Characterization of a female-specific hepatic mitochondrial cytochrome P-450 whose steady-state level is modulated by testosterone

Biochemistry ◽  
1991 ◽  
Vol 30 (34) ◽  
pp. 8323-8330 ◽  
Author(s):  
Sankar Addya ◽  
Yong Mu Zheng ◽  
Rass M. Shayiq ◽  
Jianying Fan ◽  
Narayan G. Avadhani
Keyword(s):  
Steady State ◽  
State Level ◽  
Steady State Level ◽  
Mitochondrial Cytochrome ◽  
Female Specific ◽  
Cytochrome P 450

scholarly journals Hormonal regulation of collagenolysis in uterine cervical fibroblasts. Modulation of synthesis of procollagenase, prostromelysin and tissue inhibitor of metalloproteinases (TIMP) by progesterone and oestradiol-17 β

1991 ◽  
Vol 275 (3) ◽  
pp. 645-650 ◽  
Author(s):  
T Sato ◽  
A Ito ◽  
Y Mori ◽  
K Yamashita ◽  
T Hayakawa ◽  
...  
Keyword(s):  
Steady State ◽  
Hormonal Regulation ◽  
Culture Media ◽  
Interleukin 1 ◽  
State Level ◽  
The Other ◽  
Steady State Level ◽  
Tissue Inhibitor Of Metalloproteinases ◽  
Tissue Inhibitor ◽  
Steady State Levels

Rabbit uterine cervical fibroblasts produced a large amount of matrix metalloproteinases (MMPs) such as collagenase (MMP-1) and stromelysin (MMP-3) and a small relatively amount of tissue inhibitor of metalloproteinases (TIMP). When cells were treated with progesterone or oestradiol-17 beta, both steroids concurrently decreased the level of procollagenase and prostromelysin in the culture media and the steady-state levels of the respective mRNAs. On the other hand, the level of TIMP in the culture media and the steady-state level of its mRNA were simultaneously increased by these steroids. Similarly, the suppression of production of MMPs and the augmentation of TIMP production by both steroids were observed with interleukin 1 (IL-1)-treated cells, but the action of progesterone was more effective than that of oestradiol-17 beta in the IL-1-untreated and -treated cells. These results suggest that collagenolysis in uterine cervical fibroblasts is negatively regulated by steroid hormones via the acceleration of TIMP production and the suppression of synthesis of MMPs at the pretranslational level.

Comparison of proximal tubule fluid-to-plasma ultrafiltrate chloride ratio in rats and dogs

1976 ◽  
Vol 40 (6) ◽  
pp. 1009-1011 ◽  
Author(s):  
G. R. Marchand ◽  
C. E. Ott ◽  
J. L. Cuche ◽  
F. G. Knox
Keyword(s):  
Steady State ◽  
Proximal Tubule ◽  
Species Difference ◽  
State Level ◽  
Free Flow ◽  
Steady State Level ◽  
Acid Base Balance ◽  
Significant Difference ◽  
Base Balance ◽  
Tubule Fluid

Previous studies in rats have demonstrated that the concentration of chloride in proximal tubule fluid is greater than that in plasma. The gradient reaches a free-flow steady-state level in the early proximal tubule and is maintained throughout the accessible proximal tubule. On the other hand, studies in dogs are in conflict regarding either the existence of a gradient or the development of a free-flow steady-state level. Since a species difference of tubule fluid to plasma chloride (TF/PC1) may exist, the present study was done to systematically compare the tubule fluid to ultrafiltrate chloride ratio (TF/UFC1) in hydropenic rats and dogs during normal acid-base balance. Chloride was analyzed by microelectrometric titration. In the rat the TFC1 and UFC1 concentrations were 139 +/- 1.4 and 120 +/- 1.2 meq/1, respectively. In the dog the TFC1 and UFC1 concentrations were 138 +/- 1.3 and 121 +/- 1.5 meq/1, respectively. Thus, there was no significant difference in the TF/UFC1 ratio between the rat (1.17 +/- 0.02) and the dog (1.14 +/- 0.01). Furthermore, regression analysis indicates that there is no correlation between TF/UFC1 and TF/PIn in either the rat or dog, which suggests that the gradient originates early in the proximal tubule and is maintained throughout the accessible proximal tubule in both species.

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