Activation of Protein Synthesis by Microsomes from Aging Beet Disks

The influence of Ca on the aging processes of bean stem (Phaseolus vulgaris) slices and on the absorption of K and Na by fresh and aged slices was investigated. In the presence of Ca, fresh tissue showed a preferential Na uptake. The preference for Na over K resulted from a differential depressive effect of Ca on absorption of these two ions. In aged tissue Na uptake was also depressed, but K absorption was accelerated, with a net result of a much greater absorption of K than Na.

Section: Resultsmentioning

confidence: 99%

Section: Materiais and Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Influence of Calcium on Sodium and Potassium Absorption by Fresh and Aged Bean Stem Slices

Rains¹,

Floyd²

1970

“…Although differing in detail, this phenomenon has been described in a number of systems including seed embryos induced to germinate (13,15), fertilized sea urchin eggs (8), plant storage tissues activated by excision (5,10), and mammalian cell cultures in which growth is resumed by dilution (7,11,20,25). The details of the process seem to vary for the different situations.…”

Section: Discussionmentioning

confidence: 99%

Activation of Protein Synthesis upon Dilution of an Arachis Cell Culture from the Stationary Phase

Verma¹,

Marcus²

1974

When a stationary phase cell culture of Arachis hypogaea L. is diluted into fresh media, there occurs a 10-fold increase in the rate of protein synthesis. The kinetics of the activation of amino acid-incorporating capacity show a lag of 10 to 15 minutes with maximal activity reached at 2 hours after dilu- previously described (23). Both for maintaining the culture and for experimental analyses, cells were diluted by inoculating 25 ml of a 14-day suspension into 225 ml of fresh medium.Protein Synthesis. Rates of protein synthesis were measured by incubating 10-ml aliquots of the cell suspension with 0.1 ,uc "4C-leucine (300 mc/mmole) for 5 min at 25 C. The reaction was stopped by adding 2.5 ml of cold 16% trichloroacetic acid, 1 mM leucine, and the cells were pelleted by centrifugation. The pellet was homogenized in 5 ml of 5% trichloroacetic acid, 1 mM leucine, and analyzed for hot trichloroacetic acid-insoluble radioactivity (15). In experiments where uptake of 14C-leucine was measured, the cells were harvested on Miracloth and washed with water prior to homogenization in 5% trichloroacetic acid, 1 mm leucine. An aliquot of the trichloroacetic acid-soluble radioactivity was then taken for determination of 14C leucine uptake into the soluble pool.Polyribosome Analysis. Total ribosomes were isolated by a procedure utilizing high pH for the maintenance of polyribosomal stability (1, 4). Forty-milliliter aliquots of the diluted cell suspension were harvested by filtering through Miracloth, and the cells were immediately immersed in liquid nitrogen. The frozen cells were homogenized in a mortar and pestle kept in Dry Ice and the "Dry Ice powder" of the cells was transferred to a Dounce homogenizer containing 6 ml of 20 mm KCl, 5 mm magnesium acetate, 5 mm mercaptoethanol, 150 mM tris acetate, pH 8.5, 400 mm sucrose, and 0.5% Nonidet P-40 detergent (Shell Chemical Company) (6). The cells were homogenized gently, and the slurry was passed through Miracloth to remove the whole cells and crude cell wall fragments. The homogenate was centrifuged for 10 min at 20,000g to remove nuclei and mitochondria, and the post mitochondrial supernatant was layered on 2.5 ml of 1.5 M sucrose in TKM buffer (50 mm tris, pH 8.5, 20 mm KCl, 10 mm magnesium acetate) and centrifuged for 90 min at 105,000g in a Spinco Ti 50 rotor. The pellet was dissolved in 0.5 ml of TKM buffer and any undissolved material was removed by low speed centrifugation. For analysis of polyribosome content, ribosomes equivalent to 100 jug of RNA were layered on 5 ml of 15 to 38% linear sucrose gradient in TKM buffer. The gradients were centrifuged at 50,000 rpm for 40 min in SW 50.1 rotor and fractionated as described earlier (23). For RNAase treatment, an equivalent aliquot of ribosomes was treated with 10 ,ug/ml RNAase for 10 min at 30 C and layered on the gradient as above. This unusually severe RNAase treatment was required because of the effectiveness of the TKM suspension buffer in inhibiting RNAase activity (ref. 4).Analysis of mRNA Synthesis. Twent...

“…When storage tissue is cut up into disks, developmenta,l processes are in!iitiated at the ribosomal level (5,9). In stuitable incubation conditions these bring aboutit ftundamental chaniges in metabolic activity.…”

mentioning

confidence: 99%

Further Evidence of Oxygen Diffusion as the Determining Factor in the Relation Between Disk Thickness and Respiration of Potato Tissue

MacDonald¹

1968

Abstract. The effect of oxygen tension above atmospheric pO. on the development of respiratory capacity in potato disks has been examined. Raising When storage tissue is cut up into disks, developmenta,l processes are in!iitiated at the ribosomal level (5, 9). In stuitable incubation conditions these bring aboutit ftundamental chaniges in metabolic activity. A rapid time-dependent, temperature-determined increase in respiration (13) commences soon after excision, and finalily reaches a level severa,l times greater than that obtaining in freshly cutt disks. This induced respiration of aged disks is inversely related to the thiickness of the sl,ice, the th'icker the disk the lower the respirati,on per uinit weight o,f tisstue, at least uip to 3.0 mm. This rate/thickness effect was one of the earliest observations made in tisstue disk respiration studies (19). Subsequlently, Laties (8)