Increase In Ribonucleic Acid Content Research Articles

Relation between RNA content and ageing in neurons of the dorsal lateral geniculate nucleus

We carried out a study to establish ribonucleic acid (RNA) content in the nucleus and cytoplasm of single neuronal cells from the dorsal lateral geniculate nucleus (dLGN) of 3–30 month-old rats. Mean RNA content was calculated as the product of RNA concentration and nuclear or cytoplasmic surface. The analysis of neuronal nuclei revealed no significant differences in RNA concentration, nuclear area, and RNA content from 3–18 months. However, a significant decrease in RNA concentration (18.73%) was found from the 18th–24th month, although no changes were observed in nuclear area and RNA content. The oldest rats, 24–30 months old, presented a significant increase in nuclear area and RNA content. As regards to the neuronal cytoplasm, no significant differences were found in any of the parameters at the ages from 3–18 months and 18–24 months. In contrast, a significant increase in RNA concentration (26.26%), cytoplasm area (18%), and RNA content (52%) takes place from the 24th–30th month. The increase in RNA content could be related to neuronal hypertrophy.

Influence of Cimonic Administration of Pentagastrin on the Pancreas in Hypophysectomized Rats

Hypophysectomy results in a characteristic atrophy of the pancreas. Chronic administration of pentagastrin to hypophysectomized rats results in an increase in the weight of the pancreas. This growth is accompanied by changes in the nucleic acid content of the tissue (increase in ribonucleic acid content, increase in the ratio of ribonucleic acid-deoxyribonucleic acid, and decrease in deoxyribonucleic acid concentration) which indicate an increase in the cytoplasmic content of the tissue. These changes are qualitatively similar to the changes observed in intact animals receiving similar treatment with pentagastrin. However, in hypophysectomized animals, an increase in the total content of deoxyribonucleic acid is also observed, indicating a concurrent increase in the nuclear content of the tissue. No change in acinar cell size is observed. The suggestion is put forward that in hypophysectomized rats, pentagastrin treatment stimulates pancreatic hyperplasia in addition to hypertrophy of the gland. Increase in weight of the fundus of the stomach and in a segment of duodenum is also observed. The mechanism of pentagastrin-stimulated pancreatic growth in the absence of the pituitary is discussed.

The action of insulin, growth hormone, and epinephrine on cell growth in liver, muscle, and brain of the hypophysectomized rat.

Extract: This study explores changes in deoxyribonucleic acid (DNA), ribonucleic acid (RNA), protein, and water content of muscle, liver, and cerebrum in hypophysectomized rats and the effects of injecting growth hormone, insulin, or growth hormone with epinephrine conjointly over an eleven-day period. Male hypophysectomized rats, 26 to 49 days of age, fed an ad libitum diet were studied. At 38 days of age they were injected with insulin, 0.4 to 1.8 units per day, with bovine growth hormone (250 μUg/day) or with the same amount of growth hormone and epinephrine, 5 to 20 μUg/day, concomitantly, or were untreated until the 49th day of age. Control rats of the same age were either pair-fed to untreated hypophysectomized rats or given an ad libitum diet. Untreated hypophysectomized rats showed poor body weight gain per unit food intake and reduced skeletal growth. The nucleic acid and protein content of liver, muscle, and cerebrum was reduced when compared with controls of the same age. The ratio of protein: DNA (cell size) was increased for body size but reduced for age. Administration of insulin caused hypertrophy of liver cells and increased the protein content of liver, but did not affect muscle and cerebrum. DNA content of liver or cerebrum did not increase, and the gain in DNA content of muscle was not remarkable. There was a definite increase in RNA content of muscle, liver, and cerebrum and in the ratios of RNA: DNA and protein: DNA of liver. Injections of growth hormone caused an increase in DNA (cell number), RNA, and protein content in liver, muscle, and cerebrum. There was a reduction in the ratio of cytoplasm to nucleus. The protein increment was nullified by the injection of epinephrine in conjunction with growth hormone. DNA content of muscle and liver was increased, but not to the level produced by growth hormone alone. The increase in RNA content of liver, muscle, and cerebrum was again significant; the ratio of RNA: DNA increased only in liver. Caloric intake of untreated hypophysectomized rats and those treated with growth hormone or insulin was comparable. Rats injected with epinephrine showed a significant increase in caloric intake. The results indicate that insulin is involved with growth in cell size, while growth hormone is active with respect to the increase in cell number. Both hormones are required for optimal growth. Speculation: The present study indicates that both growth hormone and insulin are required for optimum cell growth. Epinephrine administration retards the increase in cell number that normally occurs in hypophysectomized rats receiving growth hormone. This suggests that overactivity of the sympathetic pathways may retard growth and produce effects that simulate hypopituitarism.

The Increase in Ribonucleic Acid Content of Cytoplasmic Particulates of Soybean Hypocotyl Induced by 2,4-Dichlorophenoxyacetic Acid

The Increase in Ribonucleic Acid Content of Cytoplasmic Particulates of Soybean Hypocotyl Induced by 2,4-Dichlorophenoxyacetic Acid

Histochemical observations on the ribonucleic acid and glycoprotein content of the osteoclasts of the normal and ia rat

The histochemically demonstrable ribonucleic acid (RNA) and glycoprotein content of the osteoclast has been investigated in both normal and ia rats. The osteoclasts of the normal animal vary considerably in the amount of RNA present in their cytoplasm. Thus, the cells can be arranged in a series based on a progressive decrease or increase in RNA content. The majority of the osteoclasts contain an oxyphilic and pyroninophobic zone of variable width adjacent to the bone. It is suggested that the variation in RNA content might possibly be correlated with the functional state of the cell. The osteoclasts of the ia rat differ from those of the normal rat in the pattern of their RNA distribution. The predominating number of cells lack the oxyphilic, pyroninophobic zone adjacent to the bone. Since comparable results were obtained with methylene blue, pyronin and gallocyanin, it is felt that the overall decrease in thionin-positive material may be due to dye-protein interactions. The glycoprotein of the normal osteoclast is confined to sparsely scattered granules. A marked increase in the number of glycoprotein granules occurs in many of the ia osteoclasts. The significance of this increase is not apparent.

Studies on the evolution of nucleoprotein fractions of the cytoplasm during the growth of a culture of polytomella coeca: I. Ribonucleic acid content of cells and growth rate

1. 1. The chemical composition of the cytoplasmic ribonucleoprotein particles of the flagellate, Polytomella coeca, varies according to their speed of sedimentation and resembles that of the ribonucleoprotein particles of mammalian liver. 2. 2. A comparison of the Polytomella cells during the various stages of growth of a culture shows that there is no linear relationship between the quantity of ribonucleic acid per mg protein nitrogen and the rate of protein synthesis. 3. 3. The increase in ribonucleic acid content of the various nucleoprotein fractions takes place at a rate which may differ (1) from the rate of multiplication of the cells, (2) from one fraction to another.