M.S. Moruzzi

POLYAMINES and NUCLEIC ACID METABOLISM DURING DEVELOPMENT OF CHICK EMBRYO BRAIN

Abstract— Spermine and spermidine reach maximum concentrations in the chick embryo brain between the 12th and 14th day of incubation. Sucrose‐density‐gradient analysis of polyribosome distribution in the developing chick embryo brain, showed the presence of polyribosomal aggregates in the regions of 147 S and 206 S between the sixth and eighth day of incubation. After the 16th day of incubation the presence of heavier polyribosomal aggregates in the region of 259 S and 280 S was found. The injection of spermine or spermidine into the air space of embryos on the tenth day of incubation leads to a remarkable increase in the incorporation rate of [3H]formate into the ribosomes. Studies under similar experimental conditions, showed an increased radioactivity in the region of 147 S, 206 S, 259 S and 280 S in embryos injected with spermine or spermidine.

Diurnal rhythmicity of mammalian DNA-dependent RNA polymerase activities I and II: dependence on food intake.

Abstract Diurnal variations of DNA-dependent RNA polymerase activities I and II have been found in rats maintained under controlled feeding schedules. RNA polymerase I has two peaks of activity in a 24-hours cycle: one 6 hours after the onset of dark period and a second one in the middle of the light period. Polymerase II shows only one peak coinciding with the first one of polymerase I. These diurnal fluctuations are not present in the liver of rats denied food on the day of the experiment. Both polymerases do not exibit different optima for divalent metal ions and ionic strength in the different feeding conditions studied.

Evidence for a 1,25-dihydroxycholecalciferol-dependent spermine-binding protein in chick duodenal mucosa

Abstract The spermine-binding activity of a cytosol protein fraction from chick duodenal mucosa changes in relation to the circulating level of 1,25-dihydroxycholecalciferol. The spermine-binding activity increases very rapidly within 1–2 hours after the rachitic chick was dosed intracardially with 1,25-dihydroxycholecalciferol. The clear and reproducible response is prevented by actinomycin D and cycloheximide. This increase is one of the earliest events induced by the active form of vitamin D3 in the duodenal cell of rachitic chicks.

Polyamine binding by a cytoplasmic factor in the duodenal mucosa of new-born chick

Summary The incubation of micromolar concentrations of radioactive spermine with cytosol from chick duodenum leads to the formation of a non-covalent binding between spermine and a macromolecular component of the cytosol. This component seems to be a protein since trypsin but not ribonucleases can abolish the formation of the complex. The spermine-binding activity is also present in the duodenum of 18-day old chick embryo, but is dramatically lower when compared to the duodenal factor of a new-born chick.

Regulation of RNA synthesis in the liver of rats maintained under controlled feeding schedules.

It has been recently found [1] that both nucleolar and nucleoplasmic RNA synthesis measured in whole purified nuclei show daily systematic variations in the liver of rats maintained under the controlled feeding schedules developed by Potter et al. [2]. The food intake is r~sponsible for the modulation of RNA synthesis in these experimental conditions [1 ]. However it is not known whether this regulation is achieved by a larger template availability for RNA polymerase, and/or by an increased activity and/or availability of the enzyme itself. In the present paper we have evaluated the template availability of chromatin and the total amount of DNA-dependent RNA polymerase II after extraction from the liver nuclei at the times of the day in which RNA synthesis is maximal or minimal, in rats maintained under controlled feeding schedules.

Polyamines and nucleic acids in rat liver subjected to ionizing radiation

Un considerevole aumento di spermina e spermidina è stato osservato nel fegato di ratti dopo 48 h dalla pan-irradiazione con dosi totali di raggi X di 800 e di 1000 r. Gli acidi ribonucleici si modificano nello stesso modo, quantunque in misura minore.

Changes of duodenal spermine-binding activity caused by vitamin D deficiency.

Duodenal spermine-binding activity declines to a very low level during the development of chicks fed with a rachitogenic diet. A single injection of 1,25-dihydroxycholecalciferol is able to restore the activity shown by chicks fed with a normal diet.

Food-induced changes in UV-absorption spectra of isolated chromatin from liver of rats under controlled feeding schedules

We have measured the UV-spectra of liver chromatin extracted at 2 different times of day, corresponding to low or high rate of RNA synthesis from rats maintained under controlled feeding schedules. Results show that food intake does modify the UV-spectra of liver chromatin.

Functional modification of liver form-B RNA polymerase activity by a protein fraction from rats accustomed to controlled feeding schedules.

A protein fraction extracted from the liver of rats accustomed to eating during the first 8 h of a daily 12 h dark period is able to increase homologous form-B RNA polymerase activity. When the protein factor is added to RNA polymerase extracted at the end of the daily fasted period (0.9:OOh) the sensitivity of enzyme to ionic strength is modified, and resembles that of the enzyme extracted during the eating period (15:00 h) either using liver deproteinized DNA or chromatin as template. The chromatin-bound RNA polymerase activity is also modified in the presence of the factor, showing a modification of enzyme sensitivity to ionic strength similar to the one induced by food intake.

Studies on the effect of orotic acid on nucleic acid metabolism in vitamin B12-deficient chick liver

Abstract The effect of orotic acid on some aspects of nucleic acid metabolism in vitamin B12-deficient chick liver has been studied. The following results have been obtained. 1. 1. The liver of orotic acid-treated chicks showed a higher [3H]formate incorporation rate into the nuclear and ribosomal RNA. 2. 2. Polyribosomal profiles, obtained by sucrose density-gradient centrifugation, showed a higher radioactivity of the heaviest polyribosomal aggregates in the orotic acid-treated chicks. 3. 3. Nuclear DNA-dependent RNA polymerase activity showed an increased Mn 2+ ( NH 4 ) 2 SO 4 - activated reaction in the nuclei of orotic acid-treated chick liver. The results have pointed out a positive effect of orotic acid on the rapidly labeled RNA biosynthesis.