Polyadenylated RNAs as error sources in ribosomal RNA turnover analyses.

An approach to ribosomal RNA turnover studies in which cytoplasmic RNA was extracted and subsequently fractionated to isolate ribosomal RNA is reported. The presumption that the pool of 28S and 18S RNAs represented ribosomal RNA, exclusively, proved false and led to erroneous results of ribosomal RNA turnover. Polyadenylated RNAs exhibited a heterogeneous size distribution and, although constituting only 3% (w/w) of the cytoplasmic RNA extract, accounted for fully 10% of radioactivity of the presumptive ribosomal RNA pool. Profiles from the radioactivity data suggested that the discrepant results were due to these polyadenylated RNAs. An additional analytical procedure, an oligo (dT) cellulose column chromatography of the RNA extract prior to the sucrose density gradient fractionation step, performed as described in this paper, proved an effective remedy for this error.

The enzyme coupling process in urease immobilization on O-alkylated nylon tubes.

Coupling of Jack bean urease (EC 3.5.1.5) to the inside surface of type 6 nylon tubes, activated by high-temperature O-alkylation with dimethyl sulphate and modified subsequently with lysine and glutaraldehyde, was investigated to establish optimal experimental conditions for the coupling process. For the system described, the most active immobilized urease derivatives were prepared with 2 mg/ml of the solubilized urease solution and use of higher enzyme concentrations proved wasteful. Although urease coupling without thermal denaturation of the solubilized enzyme was achieved at 20 degrees C, derivatives prepared at 37 degrees C yielded maximal activity over the 3 h coupling period. Also, longer incubations of the enzyme solution in the tube were unnecessary under these conditions. Optimal pH for the coupling process was 6.5, one at which the solubilized enzyme was most stable.

On two paradoxical side-effects of prednisolone in rats, ribosomal RNA biosyntheses, and a mechanism of action.

Liver enlargement and muscle wastage occurred in Wistar rats following the subcutaneous administration of prednisolone. In the liver both the content of RNA and the biosynthesis of ribosomal RNA increased while both the RNA content and ribosomal RNA biosynthesis were reduced in the gastrocnemius muscle. It is suggested that the drug acted in a selective and tissue-specific manner to enhance ribosomal RNA synthesis in the liver and depress such synthesis in the muscle. This view supports the contention that the liver and muscle are independent sites of prednisolone action.

The effects of substrate flow-rate on immobilized urease assays.

Urease (urea aminohydrolase, EC 3.5.1.5) has been immobilized on o-alkylated nylon tubes in an enzymatically active form. The measured activity of the enzyme coil has been shown to be dependent on the flow rate of substrate through it. The apparent Km decreased and V increased as flow rates were increased. It is suggested that diffusional control is responsible for these observations. Their implications in flow-through immobilized enzyme analyses are discussed.

RNA polymerase and ribonuclease activities in skeletal muscle of prednisolone-treated rats.

Nuclei isolated from gastrocnemius muscles of rats given prednisolone acetate i.p. showed decreased levels of Mg2l-dependent RNA polymerase activity while the Mn2+-dependent polymerase activity showed no significant change from control levels. Both acid and alkaline ribonuclease activities in gastrocnemius and liver of prednisolone-treated rats were lower than levels in untreated rats. Although evidence was obtained for the existence of an inhibitor of ribonuclease activity in skeletal muscle, the effect of the glucocorticoid on ribonuclease activity was not due to increased levels of any such inhibitor.