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Biomedical subjects

R A Malt

Publications and source records attributed to R A Malt.

At least 217 records · Page 12Linked to original sources
PubMed1968

Development of the metanephric kidney. Protein and nucleic acid synthesis.

The metanephric kidney was studied in fetal and older mice beginning at 16 days after mating of the parents. Polyribosomes from fetal kidneys labeled in vitro with 14C-labeled amino acids had 10-20 times more acid-precipitable radioactivity associated with them than polysomes from adult kidneys similarly labeled. Between 3 and 6 days after birth the rate incorporation of labeled amino acids by polyribosomes from neonatal kidneys declined sharply to only twice the value found for adult kidneys. There was no change in the shape of the polyribosome profile with increasing age, but before birth few, if any, ribosomes were bound to membranes compared with 20% 2 days after birth and between 20 and 30% in the adult. Total protein represented less than 10% of the wet weight in the fetal kidney but increased to 17% of the wet weight in the adult kidney. There was a steady decline in the concentration of RNA and DNA with respect to dry weight throughout kidney development. DNA concentration declined more rapidly than RNA concentration, so that the milligram to milligram ratio of RNA to DNA increased. In males the RNA/DNA ratio was stable at 1.3 at 40 days after birth; but in females the decline in DNA concentration was more protracted, and at 200 days after birth the RNA/DNA ratio was only 0.99. Thus, total nucleic acids show only gradual changes in concentration throughout development of the kidney, but a sharp change in the synthetic activity of the ribosomes and in their binding to membranes occurs in kidneys soon after birth.

Amino Acids↗
PubMed1967

Sequential changes in classes of RNA during compensatory growth of the kidney.

The synthesis of nuclear precursors of rRNA and of cytoplasmic mRNA has been estimated in mouse kidneys following contralateral nephrectomy. 1. The production of nuclear rRNA parallels mitotic activity in the proximal tubule cells. Its peak is 2 days after nephrectomy; there may be a second peak at 8 days. 2. The production of mRNA is almost the reciprocal of rRNA production. It is least at 2 days and most at 4 days after nephrectomy. It may also decrease immediately after nephrectomy. 3. Growing kidney cells may build a store of ribosomes before they elaborate mRNA. The sequential relation between rRNA and mRNA synthesis raises the possibility that production of rRNA could regulate the production of mRNA and that the stimulus to compensatory hypertrophy might need to act only long enough to set into motion the machinery for making rRNA, either directly or as a consequence of exhausting mRNA.

Animals↗
PubMed1966

Rapidly labeled nuclear and cytoplasmic renal RNA.

Much of the RNA in mouse kidneys is not recovered when they are extracted with phenol-SDS at 60 degrees C. Better recovery is achieved by extracting in hypertonic buffer with phenol-SDS, chloroform, and isoamyl alcohol after treatment with DNase. 1. Among the polydisperse RNA in the renal nuclei are small amounts of 45S RNA and large amounts of 32S RNA; the latter first appear when 18S RNA is detectable in the cytoplasm 10 min after administration of undine-H(3). 2. In the cytoplasm rapidly labeled 18S RNA is transported as part of a 45S particle to which mRNA is attached. 3. Compared to HeLa cells in culture, normal mouse kidney is poor in the polydisperse nuclear precursors of rRNA and rich in the cytoplasmic polydisperse RNA that sediments like mRNA.

Animals↗