Decrease In RNA Content Research Articles

Morphologic Criteria of Progression and Regression of Cardiac Hypertrophy

The heart is able to adapt itself to a demanded load by increasing (hypertrophy) or decreasing (regression of hypertrophy) its muscular mass within a wide range. Overstressing of the ability of adaptation is accompanied by degenerative changes of myocytes. Semiquantitative investigations of endomyocardial biopsies (EMCBs) of patients with dilative cardiomyopathy (DCM) and hypertrophic nonobstructive cardiomyopathy (HNCM) show a fibrosis of the interstitial space, as well as almost similar changes of myofibrils and mitochondria. A reduced number of myocytes in hearts with DCM could explain the decreased functional capacity. Quantitative investigations of endomyocardial biopsies and myectomy specimens in patients with hypertrophic obstructive cardiomyopathy have revealed that hypertrophy and, to a certain extent, hyperplasia of muscle fibers cause asymmetrical thickening of the septum. Experimental investigations of the regression of training-induced hypertrophy in rats have shown that nearly all parameters (cardiac weight, thickness of muscle fibers, myofibrillar mass, interstitial space, and capillary width) returned to the values of controls 14 days after termination of a swimming training regimen. A significantly higher density of capillaries after regression of muscle fiber hypertrophy compared to controls points to a temporal dissociation in the regression of myocyte size and capillary network. Decrease in RNA concentration and an increased number of autophagic vacuoles give evidence for decreased anabolism and increased catabolism may occur during regression. In humans, fibrosis of the myocardium and scar formation explain the irreversibility of cardiac hypertrophy, as observed in some patients with valvular heart disease, despite valve replacement.

A possible role for endogenous glucocorticoids in orchiectomy-induced atrophy of the rat levator ani muscle: studies with ru 38486, a potent and selective antiglucocorticoid

We employed RU 38486, a potent and selective antiglucocorticoid, to study a possible role for endogenous glucocorticoids in atrophy of the levator ani muscle secondary to castration of male rats. RU 38486 was shown to block [ 3H]triamcinolone acetonide binding to cytosol from levator ani muscle. Daily oral administration of RU 38486 to castrated rats partially prevented atrophy of the levator ani muscle, as well as a decrease in RNA concentration. In a control group receiving RU 38486 alone, the levator ani underwent significant (20%) hypertrophy. Administration of exogenous dexamethasone also caused pronounced atrophy of the levator ani muscle. This atrophy was prevented, to a significant degree, by simultaneous oral administration of RU 38486. It is concluded that endogenous glucocorticoids, the actions of which are blocked by RU 38486, may be involved in regulation of the mass of the levator ani muscle in intact rats.

Vanadate supplements and 1,2-dimethylhydrazine induced colon cancer in mice: Increased thymidine incorporation without enhanced carcinogenesis

Because vanadate ion is a potent mitogen and accumulates in the gut of rodents fed vanadate supplements, effects of ammonium metavanadate in drinking water (10 ppm or 20 ppm) were studied on the development of large bowel neoplasms in mice treated with 1,2-dimethylhydrazine (DMH) (20 mg kg-1 weekly for 20 weeks). In the colon at 30 weeks DMH treatment caused a 14% increase in RNA content, an 18% increase in DNA content, and 33% deeper crypts. Vanadate at either 10 ppm or 20 ppm decreased RNA content by approximately 11%. Although vanadate increased thymidine incorporation 210% to 550% compared with controls, it had no influence on the attack rate, incidence, or histological type of tumours induced by DMH.

In vivo DNA synthesis in the dietary restricted long-lived rat

Male CFY Sprague-Dawley rats maintained at 50% growth rate of ad libitum fed, age-matched control animals showed a 42% extension in maximum lifespan and an increase in the overall doubling time of the rate of mortality from 102 days to 203 days. The slower growth rate of animals on the restricted diet was reflected in lower DNA, RNA, and protein c content of liver, kidney and heart with age. DNA synthesis in vivo measured by the incorporation of 3H-thymidine was severely inhibited in liver, kidney, heart, and abdominal skin, particularly during the first six months of life. The developmental peak in DNA synthesis observed in liver and kidney of ad libitum fed animals before 100 days of age was completely inhibited. No effect of restricted feeding on DNA synthesis in the small intestine was observed; however, DNA synthesis was higher in thymic tissue from the experimental animals. A decrease in RNA content of liver, kidney, and heart preceded any change in protein or DNA in animals subjected to restricted feeding. The capacity for protein synthesis (RNA/DNA ratio) was decreased by restricted feeding and was associated with a reduced protein/DNA ratio indicative of reduced cell size during the first six months of life. The translational activity per ribosome (protein/RNA ratio) was not disturbed by undernutrition in any of the tissues studied.

Effects of Retinoic Acid Versus Dimethyl Sulfoxide on Friend Erythroleukemia Cell Growth. I. Cell Proliferation, RNA Content, and Protein Content<xref ref-type="fn" rid="FN2">2</xref>

The effect of all-trans-retinoic acid (RA), an oxidative product of vitamin A, on cell growth, cell cycle kinetics, RNA content, and protein content of exponentially growing Friend erythroleukemia (FL) cells was determined and compared with the results obtained with dimethyl sulfoxide [(DMSO) CAS: 67-68-5; methyl sulfoxide], an inducer of differentiation, and alpha-difluoromethylornithine (DFMO), a potent inhibitor of ornithine decarboxylase (EC 4.1.1.17) activity. Growth inhibition of FL cells was observed only during continuous treatment with RA. While RA did not prevent growth to a high cell density, if cultures were maintained in exponential growth, cell number was reduced by 37, 67.4, and 72.2% after 6-day exposure to 10(-7), 10(-6), and 10(-5) M RA, respectively. In comparison, 280 mM (2%) DMSO and 5 mM DFMO inhibited growth over the same time course by 92 and 97.3%, respectively. DMSO resulted in an early, transient (18-24 hr) accumulation of cells in G1 phase followed by a later (5 day), irreversible accumulation of G1 cells. RA required several cell generations (48-72 hr) before a dose-dependent G1 accumulation was observed. Two populations of RA-treated FL cells could be identified: one with an intermediate RNA content (T-cells) similar to near-plateau-phase control cultures and the other with low RNA content (Q-cells) similar to that observed for DMSO-differentiated (D) cells. The kinetics of the decrease in RNA content of Q-cells paralleled those of D-cells in DMSO-treated cultures; the proportion of Q- versus T-cells in RA-treated cultures was dependent on both concentration and length of exposure. DFMO treatment did not give rise to low-RNA-containing Q-cells. Protein content of RA-treated cells was also diminished and approached that observed for hemoglobin-containing D-cells. FL cells were recoverable from long-term (greater than 5 days) treatment with RA, though 2-3 days were required for reestablishment of exponentially growing cultures; apparently only moderate RNA-containing T-cells repopulated the culture. Neither RA nor DFMO treatment gave rise to benzedine-positive, hemoglobin-containing cells as compared to DMSO that induced differentiation in these cultures.

Dietary wheat bran inhibits DNA synthesis and enhances 5-fluorouracil toxicity in rat pancreas.

The effect of a 20% wheat bran dietary supplement on pancreatic growth and on the content and synthesis of pancreatic RNA and DNA was examined in male Sprague-Dawley rats fed defined diets for 4-5 weeks. Nutrient intake and body weight gain were similar in the control group (fed a fiber-free diet) and the groups fed the wheat bran supplement. The wheat bran diet produced no significant change in pancreatic weight, protein, RNA content, or DNA content, but was associated with a 28.8% fall in pancreatic DNA synthesis, measured by [3H]thymidine incorporation into DNA, when compared with the controls (p less than 0.05). When rats were injected with 50 mg/kg of 5-fluorouracil (two injections, one week apart), those fed wheat bran exhibited a 40.1% increase in pancreatic wet weight (p less than 0.005) and a 24.5% decrease in RNA content (p less than 0.001), when compared to controls fed a fiber-free diet. RNA synthesis, measured by the incorporation of 32P into RNA, increased 3.6-fold in rats fed wheat bran, when compared with controls (p less than 0.01). These results suggest that wheat bran should be tested further for any inhibitory action on pancreatic carcinogenesis and for its modifying effect on 5-fluorouracil toxicity.

Biochemical Changes in Germinating Rice Seeds under Saline Stress

Activity of enzymes viz., amylase, ribonuclease, protease and levels of substrates like starch, sugar, RNA, protein, amino acids were studied in endosperms of germinating rice seeds under different levels of salinity. Inereased salinity decreased germination percentage, seedling growth and water uptake by endosperm. Lower concentration of NaCl caused increase in amylase activity but sharp decrease was observed with higher concentration and so was depletion of starch from endosperm. Levels of snrrose, redueing and total sugars decreased with salinity. Suppression of RNase activity and decrease in RNA content of endosperms were observed under salt treatment. The suppression of RNase activity was about 2 and 4 folds with 0.15 M and 0.30 M NaCl respectively. Salinity inhibited the rate of disappearance of protein from endosperm. Increased protease aetivity was noticed up to 48 h followed by sharp decrease during later hours of germination where maximum inhibition of activity with higher salt concentration was observed. Increase in amino acid content during early hours of germination was observed under saline situation but significant decrease was noticed during later stages of germination.

Changes of cellular markers during differentiation of HL-60 promyelocytes to macrophages as induced by T lymphocyte conditioned medium

Human promyelocytes from a cell line HL-60 of acute promyelocytic leukemia origin were examined in suspension culture in response to conditioned medium (CM) derived from allogeneic lymphocyte or phytohemagglutinin (PHA) stimulated lymphocytes. Within 24 h of exposure to CM, some cells became adherent and aggregates of cells were seen in suspension. A reduction in proliferating cells in suspension occurred, as detected by cell cycle analysis using flow cytometry. The total cellular RNA content was then reduced as determined through simultaneous fluorescence measurement of the DNA and RNA content of single cells. The cells subsequently developed a monocyte-macrophage morphology correlating with the decrease in RNA content. By day six to eight of incubation with CM, almost all the cultured cells were macrophage-like. During this development, the proportion of cells possessing complement receptors became maximal and the reactivity with alphanapthyl esterase staining and the phagocytic capacity were acquired. From these cellular changes, we can infer that the interaction between the inducer and the promyelocytes resulted in suppression of DNA replication with the parallel induction of differentiation. Activated T lymphocytes were demonstrated to be important in providing the maturation inducer. The interaction between lymphoid and promyelocytes in differentiation is discussed.

Photoperiodically induced variation in testicular RNA, DNA and protein content in hamsters and ground squirrels

1. 1. The total testicular content of RNA, DNA and protein was found to decrease sharply in hamsters with shortened photoperiod and in ground squirrels during the spring breeding season. 2. 2. RNA and DNA per g testes were found to increase in both animals, while protein per g testes remained fairly stable. 3. 3. Cell-free protein synthesis by testicular PMS during testicular regression remained constant when expressed per mg of testicular RNA, but decreased 75% when expressed per testes. 4. 4. These findings suggest that decreases in testicular protein synthesis are due to a decrease in RNA content and not to alteration of the translational activity of the RNA.

REGULATION OF RIBOSOMAL RNA SYNTHESIS DURING TAIL REGRESSION IN ORGAN CULTURE.

Tail tips of early prometamorphic larvae of Xenopus laevis were organ-cultured in Stearns' solution. Triiodothyronine induced a number of responses characteristic of metamorphosis, such as regression, decrease in DNA and RNA content, and increase in 3 H-uridine incorporation into RNA. The synthesis of ribosomal RNAs and its degradation in regressing tail tips were studied. The results obtained are: (1) the rate of transcription of ribosomal RNA, as well as the over-all rate of total RNA synthesis, does not differ between control tail tips and treated ones: (2) the 40S precursor RNA to ribosomal RNAs is processed at a higher rate in treated tips than in controls during the late period of treatment; (3) ribosomal RNAs synthesized (as well as transfer RNA) become greatly susceptible to some degradative activity in the regressing tail tips during the late period of treatment, and this may account for the observed decrease in RNA content; and (4) no evidence was obtained for the 'asymmetric' processing of the precursor molecule which has been suggested to occur in the tail muscle of prometamorphic tadpoles of Xenopus laevis.

Effect of carbon tetrachloride on RNA metabolism in the rat liver

The effect of chronic CCl4 treatment on both the liver RNA content and 3H-uridine incorporation was studied. Comparison of morphologic and biochemical parameters allowed to define two successive stages of toxic process resulting in septal fibrosis. The most significant changes in the rat liver rapid RNA turnover were observed during the first 3 months of the toxic agent action. The metabolic disturbances were also manifest in both decreased RNA content and changes of nuclear-cytoplasmic interrelationships in the damage liver tissue.

The effect of heat stress on growth and nitrogen metabolism in Friesian and F1 Brahman × Friesian heifers

Friesian and Brahman × Friesian (F1) heifers were kept in controlled environment rooms and given a high quality diet. Feed intake, growth and nitrogen metabolism were assessed during three periods of 21 days when the animals were maintained at 20, 30 or 38°C (68, 52 and 46% relative humidity respectively). The F1 animals were superior only under heat stress. Feed intakes and growth rates of Friesians and F1 animals were similar at 20°C. With each successive increase in temperature the feed intake and liveweight gain of Friesians were significantly reduced. With F1 animals the reductions were much smaller. Respiration rates and rectal temperatures of Friesians were higher than those for F1 animals at 30 and 38°C. Although the water intakes of Friesians were much higher than those of F1 animals under heat stress, the calculated evaporative water losses were similar. The efficiency of digestion in the two genotypes was similar at all temperatures. Friesians responded to increasing heat stress by increasing the nitrogen lost in urine and by decreasing nitrogen retention in relation to nitrogen intake. Similar trends for the F1 animals were much smaller. The reduction in nitrogen retention in Friesians was associated with a decrease in RNA concentration in muscle tissue and an increase in the excretion rate of creatinine.

Effects of some chelating and phenolic substances on the growth of excised pea root segments

Several chelating substances, such as 2,2'-dipyridyl, 8-hydroxyquinoline and desferal enhanced the growth of elongating segments of excised pea root tips when cultured in the presence of 2% sucrose, but their non-chelating analogues such as 4,4'-dipyridyl and 2-hydroxyquinoline were without effect. Some phenolic substances, such as cinnamic, ferulic, chlorogenic and caffeic acids, also enhanced the growth of excised segments. In general the substances which enhanced cell elongation also enhanced the development of invertase, but generally they did not enhance the increase in peroxidase activity or have any effect on the decrease in RNA content.[(14)C]cinnamic acid was continuously incorporated into the cell walls of elongating segments from which it could only be partially removed with NaOH, pronase, or HClO4. There was some evidence that the radioactivity was transferred from the cytoplasm and not incorporated directly into the cell walls. The implications of these results are discussed.

Activities of rat muscle enzymes after acute exercise.

AbstractThe enzyme activities of rat gastrocnemius and cardiac muscle were measured immediately and at varying intervals up to 5 days after exhaustive swimming to study the onset and duration of enzyme changes. Immediately after exercise a decrease in the activities of hexokinase and phosphofructokinase was found in gastrocnemius muscle. The activities of various glycolytic, hexose monophosphate shunt and oxidative enzymes were increased in both muscles 1 and 3 days and were returned to control levels after 5 days. A decrease in RNA content was obtained in cardiac muscle immediately after exercise and an increase in RNA was seen in both muscles the day after exercise. In gastrocnemius muscle glycogen overshoot was found. Glucose tolerance was increased 1 day after the exhaustive swimming. It is concluded that the intensity of exercise and the interval between exercise and enzyme analysis have to be considered when studying adaptive responses in muscle enzyme activities

PHOTOPERIODIC AGING IN ANAGALLIS ARVENSIS CLONES: ITS RELATION TO RNA CONTENT, ROOTING CAPACITY, AND FLOWERING

We investigated the photoperiodic regulation of aging in Anagallis arvensis L. propagated by cuttings. Short‐day (SD) conditions caused the persistence of juvenile forms and vegetative growth, as well as high rooting capacity and a high RNA content, through successive vegetative multiplications. SD + 1 long day (LD) every 15th day induced reproductive growth but allowed the persistence of a high rooting capacity and high RNA content through vegetative multiplications. LD conditions caused the persistence of the reproductive stage, the progressive loss of rooting capacity, and a decrease of RNA content. The longevity of the clones seems to be connected to the photoperiodic effects which induce indeterminate growth (SD) and/or determinate and reproductive growth. The loss of propagation capacity and the decrease of RNA content can be considered as indexes of aging not only in plants but also in clones.

Influence of castration on RNase activity in rat ventral prostate.

Cellular RNA content in the rat ventral prostate is decreased by castration, and therefore the influence of castration on prostatic alkaline and acid RNase activities was investigated. Castration resulted in the increase of both prostatic RNase activities pertissue protein with the resultant decrease of prostatic RNA content. RNase activities in lung or liver homogenates were not altered by the castration. Prostatic alkaline RNase activity (pH 7.9) was more sensitive to the androgen level than acid RNase activity (pH 5.5), although the latter was higher. The specific activity of alkaline RNase increased remarkably, and in a reverse relation to this, the protein content decreased in the ventral prostate after castration. Therefore, the total activity of the RNase in the prostate was hardly altered by the castration. This selective retention of the RNases would contribute to the maintenance of the RNA degradative ability during the prostate involution. Therefore, the marked decrease of RNA content in the prostate of a castrated rat would be attributed to the decline of RNA synthesizing ability and furthermore the maintenance of RNA degradative ability.

Nucleolar RNA synthesis during meiosis of lily microsporocytes.

SEVERAL authors have reported a decrease in nucleolar incorporation of 3H-uridine into RNA in male gametocytes of maize, locusts and mammals during meiotic prophase1–4, but the inactive nucleolus often persists. In the microsporocytes of Liliutn henryi the cytoplasmic ribosomes reportedly decrease in number during the extended meiotic prophase as the cellular RNA concentration also decreases5. Stern (personal communication) has also observed a decrease in RNA content in meiotic cells of Lilium longiflorum. We have examined the RNA synthetic activities of lily microsporocytes to see if the large nucleolus present is engaged in the synthesis of ribosomal RNA.

Quantitative Cytochemical Studies of RNA in Experimental Mercury Poisoning. I. Changes in RNA Content

RNA content in single spinal ganglion neurons and anterior horn motoneurons from mercury intoxicated rats were analyzed by the cytochemical method of Edstrom. The cell volume of these nerve cells was measured by Mickelwright's method. It was found that in the spinal ganglion neurons, there was a continuous decrease in the RNA content after methylmercury poisoning. After inorganic mercury (HgCl2) intoxication, there was in initial decrease in RNA content followed by a partial regaining of RNA after prolonged intoxication. These changes in RNA content were believed to be independent of the morphological changes produced by mercury in these neurons. Except for the cell swelling detected after the first week of methylmercury intoxication, there was a general decrease in cell volume after intoxication by either mercury compound. In the anterior horn motoneurons, there was a moderate increase in RNA after mercury poisoning (organic or inorganic). Since morphological lesions were only observed in the nerve fibers but not in the nerve cell bodies of these neurons, this increase in RNA level was thought to be a reparative response to the axonal injuries produced by the mercury compounds. Only a slight decrease in cell volume was observed at late stages of the intoxication.

Effect of hemicerebellectomy upon the cytochemistry of neurons in the lateral vestibular nucleus. I. Effects on RNA content and succinoxidase activity in Deiters' neurons at different post-operative intervals.

RNA content and succinoxidase activity was measured in single Deiters' giant nerve cells from the lateral vestibular nucleus in rabbits subjected to hemicerebellectomy. Postoperatively there was a decreased RNA content bilaterally after 1–2 weeks and almost restored values after 6 weeks. The succinoxidase activity showed asymmetrical changes with initially higher values on the operated side and with a rise on the contralateral side after 1 week. The succinoxidase activity and RNA content later returned to approximately preoperative values.

Experimental protein-calorie malnutrition in rats: Biochemical and ultrastructural studies

Young rats (100–130 gm) fed a low-protein diet which simulates the protein value of diets eaten by children in areas where protein-calorie malnutrition is prevalent developed many of the features associated with kwashiorkor. Among the findings were marked loss in body weight, atrophy of many visceral organs, fatty liver, hypoproteinemia, edema, and profound changes in serum amino acid patterns. Associated with the alterations in serum amino acid levels were extreme disproportions in the fasting levels of amino acids in liver. This experimental model of rodent kwashiorkor showed marked reduction in liver protein and RNA contents, but DNA remained remarkably constant indicating loss of cellular contents rather than decrease in cell population. The decreased RNA content of the liver was consistent with the observations of massive breakdown of the membranes of the endoplasmic reticulum as well as the elevated activity of alkaline ribonuclease assayed in the absence of PCMB. The polysomes showed extensive disaggregation resulting in increased monomer and dimer peaks. The significance of these biochemical and anatomical changes as well as their possible relevance to kwashiorkor in children was discussed.