scholarly journals Stable intracellular acidification upon polyamine depletion induced by α-difluoromethylornithine or N1,N12-bis(ethyl)spermine in L1210 leukaemia cells

1995 ◽  
Vol 312 (3) ◽  
pp. 749-756 ◽  
Author(s):  
R Poulin ◽  
A E Pegg
Keyword(s):  
Steady State ◽  
Acid Stress ◽  
Weak Acid ◽  
Transport Processes ◽  
Set Point ◽  
L1210 Cells ◽  
Acid Load ◽  
Mouse Leukaemia ◽  
A Minor ◽  
Steady State Control

Polyamines play major roles in ionic and osmotic regulation, but their exact involvement in specific ion transport processes is poorly defined. Treatment of L1210 mouse leukaemia cells with either 5 mM alpha-difluoromethylornithine (DFMO), a suicide substrate of ornithine decarboxylase, or 25 microM N1,N12-bis(ethyl)spermine (BE-3-4-3), a dysfunctional polyamine analogue, caused a stable decreased in intracellular pH (pHi) by 0.1-0.4 unit from steady-state control values between 7.4 and 7.6, as measured either by partition of a weak acid or with a fluorescent pH-sensitive probe. This effect was not related to cell growth status or differences in metabolic acid generation, and was observed in either the presence or absence of HCO3-. Exogenous spermidine (10-25 microM) or putrescine (25-50 microM) fully reversed DFMO- or BE-3-4-3-induced acidification within 2 and 8 h respectively. Recovery of pHi in L1210 cells after a nigericin- or NH4(+)-mediated acid load in HCO3(-)-free buffers was mediated by Na+/H+ antiporter activity, in addition to a minor Na(+)-independent and amiloride-insensitive pathway. Decreased steady-state pHi was maintained in polyamine-depleted L1210 cells after recovery from acid stress. Moreover, the pHi-dependence of the rate of Na(+)-dependent H+ extrusion after an acid stress was altered by DFMO and BE-3-4-3, resulting in a set-point which was lower by 0.25-0.30 pH unit in polyamine-depleted cells. On the other hand, neither the rate nor the magnitude of Na+/H(+)-exchanger-mediated alkalinization induced by hypertonic shock was decreased by polyamine depletion. Thus polyamine depletion induces a persistent defect in pHi homeostasis which is due, at least in part, to a stable decrease in the pHi set-point of the Na+/H+ exchanger.

Control of an adiabatic continuous reactor by feeding catalyst

1980 ◽  
Vol 45 (11) ◽  
pp. 2903-2918 ◽  
Author(s):  
Josef Horák ◽  
Zina Valášková ◽  
František Jiráček
Keyword(s):  
Steady State ◽  
Reaction Temperature ◽  
Continuous Reactor ◽  
Control Element ◽  
Inlet Temperature ◽  
Switching Cycle ◽  
Point Temperature ◽  
Set Point ◽  
Constant Rate ◽  
Laboratory Reactor

Algorithms have been presented, analyzed and experimentally tested to stabilize the reaction temperature at constant inlet temperature and composition of the feed by controlled dispensing of the catalyst. The information for the control element is the course of the reaction temperature. If the temperature of the reaction mixture is below the set point, the catalyst is being fed into the reactor at a constant rate. If the reaction temperature is higher the catalyst dispenser is blocked; dispensing of the catalyst is not resumed until the set point temperature has been reached again. The amount of catalyst added is a function of the duration of the switching cycle. The effect has been discussed of the form of this function on the course of the switching cycle. The results have been tested experimentally on a laboratory reactor controlled in an unstable steady state.

Role of glucose in corneal metabolism

1985 ◽  
Vol 249 (5) ◽  
pp. C409-C416 ◽  
Author(s):  
R. S. Thies ◽  
L. J. Mandel
Keyword(s):  
Oxygen Consumption ◽  
Steady State ◽  
Specific Activity ◽  
Krebs Cycle ◽  
Lactate Production ◽  
Minor Component ◽  
Acid Oxidation ◽  
Endogenous Fatty Acid ◽  
Nonsteady State ◽  
A Minor

Glucose catabolism by glycolysis and the Krebs cycle was examined in the isolated rabbit cornea incubated with [6-14C]glucose. The production of [14C]lactate and 14CO2 from this substrate provided minimal values for the fluxes through these pathways since the tissue was in metabolic steady state but not isotopic steady state during the 40-min incubation. The specific activity of lactate under these conditions was one-third of that for [6-14C]glucose, and label dilution by exchange with unlabeled alanine was minimal, suggesting that glycogen degradation was primarily responsible for this dilution of label in the Embden-Meyerhof pathway. In addition, considerable label accumulation was found in glutamate and aspartate. Calculations revealed that these endogenous amino acid pools were not isotopically equilibrated after the incubation period, suggesting that they were responsible for the isotopic nonsteady state by exchange dilution through transaminase reactions with labeled intermediates. An estimate of glucose oxidation by the Krebs cycle, which was corrected for label dilution by exchange, indicated that glucose could account for most of the measured corneal oxygen consumption that was coupled to oxidative phosphorylation. A minor component of this respiration could not be accounted for by glucose or glycogen oxidation. Additional experiments suggested that endogenous fatty acid oxidation was probably also active under these conditions. Finally, reciprocal changes in plasma membrane Na+-K+-ATPase activity induced by ouabain and nystatin were found to concomitantly alter oxygen consumption rates and [14C]lactate production from [6-14C]glucose. These results demonstrated the capacity for regulating glycolysis and the Krebs cycle in response to changing energy demands in the cornea.

Intracellular pH transients in rat diaphragm muscle measured with DMO

1978 ◽  
Vol 235 (1) ◽  
pp. C49-C54 ◽  
Author(s):  
A. Roos ◽  
W. F. Boron
Keyword(s):  
Intracellular Ph ◽  
Weak Acid ◽  
Diaphragm Muscle ◽  
Disulfonic Acid ◽  
Free Solution ◽  
Rat Diaphragm ◽  
Control Value ◽  
Acid Load ◽  
Acid Extrusion ◽  
Acid Loading

Changes of the intracellular pH of rat diaphragm muscle were monitored at 30-min intervals with the weak acid DMO (5,5-dimethyl-2,4-oxazolidinedione). Transferring the muscle from a CO2-containing to a CO2-free solution caused intracellular pH (pHi) to rise by an average of 0.18 during the first 30 min and then to level off at a slightly lower value over the next 60-90 min. Transferring the muscle from a CO2-free to a CO2-containing solution caused pHi to fall by 0.18 during the first 30 min and then to recover by 0.05 over the next 90 min. Subsequent return to the CO2-free solution caused pHi to overshoot the control value by 0.10. Both the recovery and the overshoot can be accounted for by an acid-extruding pump. Intracellular acid loading with 118 mM DMO similarly caused pHi to fall initially, to recover slowly during the acid loading, and then to overshoot the control pHi on removal of the acid load. In the absence of HCO3-/CO2, acid extrusion was reduced by about a fifth. SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid) had no effect. The absence of either Na+ or Cl- from HCO3-/CO2- free solution reduced acid extrusion by about a half.

scholarly journals APLIKASI KONTROL PID PADA PROSES PENGOLAHAN AIR LAUT MENGGUNAKAN METODE REVERSE OSMOSIS BERBASIS DCS

JURNAL ELTEK ◽  
2019 ◽  
Vol 17 (2) ◽  
pp. 32
Author(s):  
Hariyadi Singgih Singgih ◽  
Subiyantoro Subiyantoro ◽  
Siswoko Siswoko
Keyword(s):  
Steady State ◽  
Reverse Osmosis ◽  
Rise Time ◽  
Delay Time ◽  
Settling Time ◽  
Set Point ◽  
Pressure Transmitter

Metode pemurnian air laut menggunakan pengaturan kecepatan motor dalam proses reverse osmosis sangat dibutuhkan, dikarenakan proses penyaringan dalam membran reverse osmosis membutuhkan tekanan yang sesuai dengan kemampuan membran. Selain itu juga dibutuhkan kontrol ketinggian air untuk mengotomatisasi tangki yang telah penuh dan mempertahankan ketinggian air. Solusi untuk mengurangi permasalahan ini digunakan DCS yang berfungsi untuk memonitor dan mengontrol plant dari jarak jauh, Metode kontrol yang digunakan pada DCS untuk menstabilkan set point menggunakan metode kontrol PID Ziegler-Nichols. Dalam penelitian ini dirancang mini plant kontrol ketinggian air dan tekanan menggunakan metode PID Ziegler-Nichols yang diimplementasikan pada DCS-PCS7. Sensor yang digunakan untuk ketinggian air adalah HC-SR04, dan untuk sensor tekanan menggunakan pressure transmitter. Dengan aplikasi kontrol PID diperoleh kestabilan set point dengan parameter kontrol ketinggian air : Kp=134.4, Ti=0 dan Td=1. Waktu untuk mencapai set point 120 detik dan  error steady state sebesar 0.94% tanpa gangguan. Untuk parameter Kontrol tekanan air sebesar: Kp=3, Ti=0 dan Td=1.375 dan Delay time = 4s, Rise time = 7s, Settling time = 25s, Osilasi output PID rendah, Error steady state = 1.03% tanpa gangguan.    

scholarly journals Pengkondisian Suhu Air Perebusan Kedelai Pada Pembuatan Tempe Dengan Metode PID

2021 ◽  
Vol 6 (3) ◽  
pp. 40
Author(s):  
Siroju Insan ◽  
Tarmukan Tarmukan ◽  
Mila Fauziyah
Keyword(s):  
Steady State ◽  
Rise Time ◽  
Delay Time ◽  
Set Point

Tempe merupakan makanan tradisional yangpopuler di Indonesia. Salah satu bahan dari tempe adalahkacang kedelai. Cara pembuatannya terdiri dari pengupasan,perebusan, inokulasi, dan peragian. Proses perebusandilakukan dengan merebus kedelai ke dalam air dengan suhutertentu. Tujuan perebusan ialah sebagai proses hidrasi agarkedelai dapat menyerap air sebanyak mungkin. Prosesperebusan yang umum digunakan saat ini masih manualsehingga hasilnya kurang maksimal. Hal ini karena suhu dariproses perebusan secara manual tidak stabil. Oleh karena itu,penelitian ini dilakukan untuk mengontrol suhu pada prosesperebusan agar tetap stabil. Penelitian ini menggunakanmetode kontrol PID untuk mengatur suhu dengan caramengatur besar bukaan valve gas LPG pada tungku. Suhu daritungku dideteksi menggunakan sensor suhu RTD PT100 untukdibandingkan dengan nilai set point. Dengan menggunakanmetode Ziegler-Nichols didapatkan nilai penguatan Kp=50.64,Ki=1.266, dan Kd= 506.4. Dari nilai konstanta Kp, Ki, dan Kdtersebut diperoleh respon output dengan nilai nilaiOvershoot=0.4%, delay time=7.19, rise time=14.38, settlingtime=15.06, error steady-state (atas)=0.67%, dan errorsteady-state (bawah)=1.78%.

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