Svetozar Petrović

Retention of ribosomal ribonucleic acids in agarose gels.

Abstract Ribosomal RNAs from various organisms could be immobilized in agarose gels at high ionic strength in a thermally reversible fashion. In NaCl solutions at 23 °C, agarose capacity for retention of liver rRNAs was about 0.4 mg/ml gel under saturating conditions. NaCl molarities necessary for a 50 % retention of rat liver rRNAs increase with temperature (in the range of 23–37 °C) by 0.04–0.05 M/degree for the larger (28-S) component, and by 0.07–0.09 M/degree for the smaller (18-S) component. The retention process also displays cation selectivity; for rat liver 28-S RNA, molarities of alkali metal chlorides at 50 % retention and 23 °C were: LiCl and NaCl, about 0.4 M; KCl, about 0.6 M; CsCl, about 0.9 M. The retention molarities of NaCl tend to decrease with increase in both the molecular weight and the G + C content of rRNAs, but the relationship of these variables is clearly non-linear, and it might depend on undetermined features of rRNA structure. The retention profiles appear to be largely characteristic of respective species of rRNAs.

Separation of ribosomal RNAs on agarose gels

Abstract 28-S ribosomal RNA of rat liver is selectively retained in highly hydrated ‘sphere-condensed’ agarose gels equilibrated at 21–25° with a sodium dodecyl sulfate-Tris-EDTA buffer containing 0.5 M NaCl. The adsorbed or gelated polynucleotide could be recovered by elution with 0.1 M NaCl in the same buffer, or by raising the temperature to 35°. The density gradient profiles and nucleotide compositions indicate that the separation under the described conditions is close to being quantitiative.

Segments of 28-S RNA protected from pancreatic ribonuclease by interaction with ribosomal proteins.

Abstract About 10 % of 28-S rRNA could be protected from the exhaustive action of pancreatic ribonuclease (EC 2.7.7.16), but not from T1 ribonuclease (EC 2.7.7.26) by a specific interaction with ribosomal proteins. The average chain length of the protected material is 28 nucleotidyl residues. Its nucleotide composition (C, 20.9±0.6; A, 16.5±0.4; U, 10.3±0.2; G, 52.3±0.9) is distinctively different from either 28-S RNA or from rRNA “cores”. The dissociation of protected material from ribosomal proteins occurs in the 0.5–1.25 M range for alkaline chlorides, and exhibits some cation selectivity ( Li ≧ Na > K > Cs ). Competition with free rRNA and determination of ribonuclease sensitivity of RNA in partially deproteinized ribosomes indicate that a significant fraction of the protected 28-S RNA segments could be in situ associated with ribosomal proteins.

Isolation of nuclear rapidly sedimenting ribonucleic acids by agarose gel filtration

Abstract Gel filtration of rat liver nuclear RNAs on Sepharose 4B permits routine separation of the rapidly sedimenting (30–60S) ribopolynucleotides from ribosomal RNAs. The method could be easily adapted to either analytical characterization or preparative isolation of preribosomal and polycistronic RNAs.

Increased β-adrenergic receptor complement in androgen-induced mouse kidney hypertrophy

Treatment of female mice with testosterone propionate led to a pronounced, but gradual increase in kidney beta-adrenergic receptor complement. The specific binding of [125I]iodohydroxybenzylpindolol rose 2-3-fold above the control levels after 8-12 days of the treatment. No significant changes were detected prior to the fourth day of androgen administration. No gross changes in either the binding strength or cooperativity of the binding were apparent in membrane preparations from treated animals. Averages of the high-affinity binding constant estimates were 1.3 +/- 0.3 nmol in controls, vs. 1.6 +/- 0.5 nmol in treated animals (15 groups each) in competition with pindolol, with the Hill slope factors of 0.98 +/- 0.08 for controls, and 0.91 +/- 0.07 for the treated animal membrane preparations. Scatchard estimates of the binding constants in self-competed [125I]iodohydroxybenzylpindolol binding were about 160 pmol in both control and treated animals. Competition experiments using isoproterenol also indicated similar dissociation constants (151 +/- 16 nmol) for control and treated groups. Na+/K+-activated ATPase (EC 3.6.1.3) was also found to be increased at the 12th day of the androgen treatment (to 74% above control levels).

DIFFERENT TURNOVER RATES OF BRAIN RIBOSOMAL RIBONUCLEIC ACIDS IN MALE AND FEMALE RATS

Abstract— Following a single intracranial injection of [5‐3H]orotic acid, the decay dynamics were determined for rRNAs of whole brain in male and female Wistar‐inbred albino rats aged 2.5‐3.5 months. The turnover rate for male brain rRNAs was significantly lower than in females (mean half‐lives being, respectively, 12.2 ± 2.2 (S.D.M.) days, and 7.4 ± 1.3 days in four regression measurements). This difference was apparently not related to the turnover rate of acid‐soluble brain nucleotides, which turned over much faster and at a similar rate in rats of both sexes; it also could not be connected with brain levels of rRNAs or DNAs, which were quite similar For males and females. The results are discussed in terms of possible sex hormone determination of brain RNA metabolic patterns especially in males.