scholarly journals Stimulation of Derepressed Enzyme Synthesis in Bacteria by Growth on Sublethal Concentrations of Chloramphenicol

1975 ◽  
Vol 7 (5) ◽  
pp. 555-563 ◽  
Author(s):  
S. R. Ford ◽  
R. L. Switzer
Keyword(s):  
Enzyme Synthesis ◽  
Sublethal Concentrations ◽  
Stimulation Of

Study on the inactivation of enzymes in Jerusalem artichoke tuber slices

1972 ◽  
Vol 50 (4) ◽  
pp. 727-731 ◽  
Author(s):  
Marcel Bastin ◽  
Osman Ünlüer
Keyword(s):  
Half Life ◽  
Jerusalem Artichoke ◽  
Phenol Oxidase ◽  
Enzyme Synthesis ◽  
Strong Inhibitor ◽  
First Order ◽  
Jerusalem Artichoke Tuber ◽  
Enzyme Degradation ◽  
Inhibitor Of Protein Synthesis ◽  
Stimulation Of

The formation of both peroxidase and phenol oxidase was induced by culturing slices of Jerusalem artichoke tubers under aerobic conditions at 30 °C. The rate of enzyme degradation in the tuber slices was measured after applying cycloheximide, a strong inhibitor of protein synthesis, or by culturing the tissues under anaerobic conditions. Peroxidase decayed according to a first order process with a half-life of 8.3 h while phenol oxidase was found to be more stable (half-life about 70 h). The increase in the level of enzymes after the slicing treatment was achieved through a stimulation of the rate of enzyme synthesis rather than a decrease in the rate of destruction.

scholarly journals Regulation of S-adenosylmethionine decarboxylase by polyamines in Ehrlich ascites-carcinoma cells grown in culture

1980 ◽  
Vol 190 (3) ◽  
pp. 747-754 ◽  
Author(s):  
Leena Alhonen-Hongisto
Keyword(s):  
Half Life ◽  
Ehrlich Ascites Carcinoma ◽  
Enzyme Synthesis ◽  
Tumour Cells ◽  
Transcriptional Level ◽  
Decarboxylase Activity ◽  
Adenosylmethionine Decarboxylase ◽  
Ehrlich Ascites ◽  
Ehrlich Ascites Tumour ◽  
Stimulation Of

1. The mechanism of stimulation of S-adenosylmethionine decarboxylase (EC 4.1.1.50) activity by inhibitors of ornithine decarboxylase (EC 4.1.1.17), namely dl-α-difluoromethylornithine, 1,3-diaminopropane and 1,3-diaminopropan-2-ol, was studied in Ehrlich ascites-tumour cells grown in suspension cultures. 2. Difluoromethylornithine and diaminopropane, although decreasing the content of putrescine and spermidine, markedly stimulated adenosylmethionine decarboxylase activity after exposure of the cells to the drugs for 8h, whereas the effect of diaminopropanol only became apparent many hours later. In tumour cells exposed to any of the inhibitors, a close negative correlation existed between the activity of adenosylmethionine decarboxylase and the intracellular concentration of spermidine and/or spermidine plus spermine, suggesting that a depletion of higher polyamines triggered enhancement of adenosylmethionine decarboxylase activity. 3. The mechanism of difluoromethylornithine- and diaminopropane-induced stimulation of adenosylmethionine decarboxylase involved (a) a marked increase in the apparent half-life of the enzyme and (b) an induction of enhanced enzyme synthesis. Diaminopropanol seemed to act solely via an induction mechanism. 4. The increased adenosylmethionine decarboxylase activity elicited by difluoromethylornithine could be restored to control values by micromolar concentrations of exogenous spermidine and spermine in 4h and by putrescine in 22h. In addition to the natural polyamines, elevated adenosylmethionine decarboxylase activity could be repressed by 3,3′-iminodipropylamine, a close analogue of spermidine, but not by non-physiological diamines. 5. Addition of spermidine and actinomycin D to cultures treated with difluoromethylornithine produced a comparable decay of enhanced adenosylmethionine decarboxylase activity (with an apparent half-life of about 2.5h), whereas the effect of cycloheximide was much more rapid. The present results suggest that polyamines may regulate adenosylmethionine decarboxylase at the transcriptional level of gene expression.

Electrolyte balance and enzyme synthesis pattern in rat salivary glands and pancreas

1959 ◽  
Vol 196 (2) ◽  
pp. 365-367 ◽  
Author(s):  
L. H. Schneyer ◽  
C. A. Schneyer
Keyword(s):  
Parotid Gland ◽  
Salivary Glands ◽  
Enzyme Synthesis ◽  
Potassium Content ◽  
Electrolyte Balance ◽  
Prolonged Stimulation ◽  
Rat Salivary Glands ◽  
Short Period ◽  
Sodium And Potassium ◽  
Stimulation Of

Sodium and potassium content and water/dry ratios have been determined for unstimulated and stimulated rat salivary glands and pancreas. Results are correlated with time in the ‘secretion cycle’ of increased amylase synthesis. Increased amylase synthesis by submaxillary and sublingual glands promptly follows the onset of stimulation but is delayed in parotid gland and pancreas by a dependence on gland amylase depletion. Unstimulated submaxillary and sublingual glands from fasted animals have a relatively low Na/K ratio which rises during short-period pilocarpine stimulation, due to loss of K and gain of Na. This increased Na/K ratio is not maintained in these glands during prolonged stimulation but is present during the period of accelerated amylase synthesis. The resting parotid gland has a high Na/K ratio which is reduced during stimulation, due to loss of Na, approximately to the level observed for active submaxillary and sublingual glands. This ratio is maintained during prolonged stimulation of parotid gland. The pancreas presents certain differences from the parotid gland in electrolyte levels, but the patterns of change with stimulation agree generally.

Insulin action in pancreatic acini from streptozotocin-treated rats. I. Stimulation of protein synthesis

1981 ◽  
Vol 240 (1) ◽  
pp. G56-G62 ◽  
Author(s):  
M. Korc ◽  
Y. Iwamoto ◽  
H. Sankaran ◽  
J. A. Williams ◽  
I. D. Goldfine
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Cell Concentration ◽  
Enzyme Synthesis ◽  
Detectable Effect ◽  
Leucine Incorporation ◽  
Maximal Effect ◽  
Pancreatic Acini ◽  
Pancreatic Exocrine ◽  
Stimulation Of

Pancreatic acini were prepared from rats rendered diabetic with streptozotocin. In this tissue, insulin stimulated [3H]leucine incorporation into protein. The full effects of insulin on this function were not immediate but increased linearly with time for up to 2 h of incubation. Insulin had a detectable effect on l eucine incorporation at 50 pM, a half-maximal effect at 0.7 nM, and a maximal effect at 30 nM. Desdipeptide proinsulin was only 10% as potent as native insulin in stimulating [3H]leucine incorporation, whereas proinsulin and desoctapeptide insulin were only 1% as potent. Insulin also increased the incorporation of [3H]valine and [35S]methionine into protein but did not increase the influx of either [14C]cycloleucine or alpha-[3H]aminoisobutyric acid. These observations suggested that the increased incorporation of labeled amino acid into protein reflected stimulation of protein synthesis rather than stimulation of amino acid transport. Furthermore, insulin at 1.67 nM significantly increased the acinar cell concentration of amylase. The present findings are consistent therefore with the concept that insulin regulates pancreatic exocrine functions, including protein and enzyme synthesis.

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