ABSTRACT
Neonatal thyroidectomy impairs, at 10 days of age, the [quot ]in vivo[quot ] specific activity of brain [quot ]rapidly-labeled[quot ] RNA, both in nuclei and microsomes. The labeling of ribosomal RNA, whose nuclear synthesis is not affected by hypothyroidism, appears diminished at the microsomal level, indicating an impairment of transport across the nuclear membranes. [quot ]Rapidly-labeled[quot ] RNA values did not change under the same conditions. Underfeeding causes the same changes as thyroidectomy on the labeling and transport of cerebral RNA, with the only exception of the nuclear mRNA release, which is diminished by undernourishment. The alterations of cytosolic factors cause the impairment of cerebral ribosomal RNA release in hypothyroid rats, while changes in unknown intranuclear mechanisms are responsible for the decreased transport of ribosomal RNA in undernourished rats.
ABSTRACT
Neonatal thyroidectomy impairs, at 10 days of age, the "in vivo" specific activity of brain "rapidly-labeled" RNA, both in nuclei and microsomes. The labeling of ribosomal RNA, whose nuclear synthesis is not affected by hypothyroidism, appears diminished at the microsomal level, indicating an impairment of transport across the nuclear membranes. "Rapidly-labeled" RNA values did not change under the same conditions. Underfeeding causes the same changes as thyroidectomy on the labeling and transport of cerebral RNA, with the only exception of the nuclear mRNA release, which is diminished by undernourishment. The alterations of cytosolic factors cause the impairment of cerebral ribosomal RNA release in hypothyroid rats, while changes in unknown intranuclear mechanisms are responsible for the decreased transport of ribosomal RNA in undernourished rats.
Subject(s)
Brain/metabolism , Hypothyroidism/physiopathology , Protein-Energy Malnutrition/physiopathology , RNA/metabolism , Animals , Biological Transport , Cell-Free System , Cytosol/metabolism , Nuclear Envelope/metabolism , Protein Deficiency/metabolism , Rats , Rats, Inbred Strains , Thyroid Hormones/deficiencyABSTRACT
Neonatal thyroidectomy impairs, at 10 days of age, the [quot ]in vivo[quot ] specific activity of brain [quot ]rapidly-labeled[quot ] RNA, both in nuclei and microsomes. The labeling of ribosomal RNA, whose nuclear synthesis is not affected by hypothyroidism, appears diminished at the microsomal level, indicating an impairment of transport across the nuclear membranes. [quot ]Rapidly-labeled[quot ] RNA values did not change under the same conditions. Underfeeding causes the same changes as thyroidectomy on the labeling and transport of cerebral RNA, with the only exception of the nuclear mRNA release, which is diminished by undernourishment. The alterations of cytosolic factors cause the impairment of cerebral ribosomal RNA release in hypothyroid rats, while changes in unknown intranuclear mechanisms are responsible for the decreased transport of ribosomal RNA in undernourished rats.
ABSTRACT
A method to measure the "in vitro" RNA release from rat brain cell nuclei was described. Nuclear RNA was prelabelled "in vivo" for 30 or 120 min. In the first case the released RNA was heterogeneous and its electrophoretic mobility was similar to that of cytoplasmic messenger RNAs; nuclei prelabelled for 120 min mostly released the two major species of ribosomal RNAs. The release of mRNAs from the nuclei increased during cerebral development while that of the ribosomal RNAs did not. The increased capacity of the nuclei to release "radidly labelled" RNA with age neither determined an increase of the polysomal population, nor seemed to be dependent on cytoplasmic macromolecules.
Subject(s)
Brain/metabolism , Cell Nucleus/metabolism , RNA/metabolism , Adenosine Triphosphate/metabolism , Animals , Brain/growth & development , Brain/ultrastructure , Female , In Vitro Techniques , Male , Methods , Rats , TemperatureABSTRACT
The effects of neonatal thyroidectomy on the incorporation in vivo of labelled orotic acid into acid-soluble uridine nucleotides, nuclear RNA and microsomal RNA of the rat brain were studied at 10 and 30 days of age. It was found that the conversion of orotate into uridine nucleotides is high at the earliest stage and does not change upon maturation. At any stage, the neonatal lack of thyroid function does not effect the conversion of orotate into uridine nucleotides. Neonatal thyroidectomy led to a significant decrease in the synthesis of cerebral RNA only at 10 days after birth.
Subject(s)
Brain/metabolism , Hypothyroidism/metabolism , RNA/biosynthesis , Uridine/biosynthesis , Age Factors , Animals , Orotic Acid/metabolism , Rats , Thyroid Gland/metabolism , ThyroidectomyABSTRACT
The effects of neonatal thyroidectomy on the incorporation in vivo of labelled orotic acid into acid-soluble uridine nucleotides, nuclear RNA and microsomal RNA of the rat brain were studied at 10 and 30 days of age. It was found that the conversion of orotate into uridine nucleotides is high at the earliest stage and does not change upon maturation. At any stage, the neonatal lack of thyroid function does not effect the conversion of orotate into uridine nucleotides. Neonatal thyroidectomy led to a significant decrease in the synthesis of cerebral RNA only at 10 days after birth.
ABSTRACT
The effects of neonatal thyroidectomy on the incorporation in vivo of labelled orotic acid into acid-soluble uridine nucleotides, nuclear RNA and microsomal RNA of the rat brain were studied at 10 and 30 days of age. It was found that the conversion of orotate into uridine nucleotides is high at the earliest stage and does not change upon maturation. At any stage, the neonatal lack of thyroid function does not effect the conversion of orotate into uridine nucleotides. Neonatal thyroidectomy led to a significant decrease in the synthesis of cerebral RNA only at 10 days after birth.
