RNA-DNA Ratio Research Articles

Field and Laboratory Determinations of Hypoxic Effects on RNA-DNA Ratios of Bluegill

We used RNA-DNA ratios in both field and laboratory experiments to examine the effects of hypoxia on short-term growth of bluegill Lepomis macrochirus collected from the lower Atchafalaya River Basin, Louisiana. In the field experiment, RNA-DNA ratios of bluegill (17.8–52.3 g) from hypoxic habitats (DO < 2.0 mg L−1; n = 26) were significantly lower than ratios of bluegill from normoxic habitats (DO > 4.0 mg L−1; n = 31). In each of two laboratory experiments 40 bluegill (14.54–76.70 g) were individually placed in aquaria to test the effects of hypoxia on RNA-DNA ratios. Additionally, bluegill were fed at different rates in the first experiment to determine the effects of feeding level on RNA-DNA ratios. Results of the first experiment confirmed the sensitivity of RNA-DNA ratios to short-term changes in growth, as fed bluegill had significantly higher ratios than starved bluegill. In both experiments RNA-DNA ratios were not significantly different in bluegill subjected to hypoxia. Results of the study indicate that laboratory experiments did not adequately simulate increased bioenergetic demands and fluctuating DO levels found in hypoxic areas of the Basin.

Variation Among Four Health Indices in Natural Populations of the Estuarine Fish, Fundulus heteroclitus (Pisces, Cyprinodontidae), from Five Geographically Proximate Estuaries

Variation among four commonly used health indices was examined in the mummichog, Fundulus heteroclitus. The four indices were liver glycogen content (LGC), liver-somatic index (LSI), condition index (K) and RNA–DNA ratio. Fish were collected from five coastal locations in southeastern Connecticut. Fish health, as determined by these four indices, varied considerably among estuaries and between sexes. The relationship between each index and specimen length was significantly different among estuaries for either sex. When regressed against length, the slopes for the indices ranged from positive to negative. For each index, significant differences existed among some of the length-centered means at each estuary for either sex. Estuary rank for one index did not necessarily correlate with the estuary rank for another index. The significance of this variability and its impact on the use of the indices as bioindicators of environmental perturbation is discussed.

Lovastatin prevents angiotensin II-induced cardiac hypertrophy in cultured neonatal rat heart cells

Angiotensin II activates p21 ras, and mediates cardiac hypertrophic growth through the type 1 angiotensin II receptor in cardiac myocytes. An inhibitor of 3-hydroxy-3-methyglutaryl-coenzyme A (HMG-CoA) reductase has been shown to block the post-translational farnesylation of p21 ras and inhibit protein synthesis in several cell types. Primary cultures of neonatal cardiac myocytes were used to determine whether HMG-CoA reductase inhibitors, lovastatin, simvastatin and pravastatin inhibit the angiotensin II-induced hypertrophic growth. Angiotensin II (10 −6 M) significantly increased protein–DNA ratio, RNA–DNA ratio, ratios of protein synthesis and mitogen-activated protein (MAP) kinase activity. Lipid-soluble HMG-CoA reductase inhibitors, lovastatin (10 −6 M) and simvastatin (10 −6 M) partially and significantly inhibited the angiotensin II-induced increases in these parameters, but a water-soluble HMG-CoA reductase inhibitor, pravastatin (10 −6 M) did not. Mevalonate (10 −4 M) overcame the inhibitory effects of lovastatin and simvastatin on angiotensin II-induced increases in these parameters. A selective protein kinase C inhibitor, calphostin C (10 −6 M) partially and significantly prevented angiotensin II-induced increases in these parameters, and treatment with both lovastatin and calphostin C inhibited completely. Angiotensin II increased p21 ras activity and membrane association, and lovastatin inhibited them. These studies demonstrate that a lipid-soluble HMG-CoA reductase inhibitor, lovastatin, may prevent angiotensin II-induced cardiac hypertrophy, at least in part, through p21 ras/MAP kinase pathway, which is linked to mevalonate metabolism.

RNA–DNA ratios in white muscle tissue biopsies reflect recent growth rates of adult brown trout

RNA–DNA ratios in white muscle tissue biopsies reflect recent growth rates of adult brown trout

RNA‐DNA ratios in white muscle tissue biopsies reflect recent growth rates of adult brown trout

Recently developed fluorescence techniques were used to quantify RNA‐DNA ratios in white epaxial muscle tissue biopsies taken from live adult brown trout. RNA‐DNA ratios from small biopsies (4–24 mg wet weight) were measured concurrently with growth over 5 weeks in two groups of brown trout fed different rations, 5% BW day– 1 (reference) and 1% BW week– 1(treatment). Reduced rations had significant effects on RNA‐DNA ratios in muscle tissue biopsies. The treatment group had significantly lower mean RNA–DNA ratios than the reference group after the first week. After 5 weeks of treatment the mean RNA–DNA ratios of the treatment and reference groups were 1–98 and 4–31, respectively. RNA‐DNA ratios from muscle tissue biopsies reflected recent growth rates in the two groups of fish. This technique allows a biochemical measurement of growth rates in adult fish without mortality.

Nucleic acid levels, cellular activity and growth during the puerulus stage of the Western Rock Lobster ( Panulirus cygnus (George); Decapoda: Palinuridae)

The potential impact of non-feeding in pueruli of the Western Rock Lobster Panulirus cygnus (George; Decapoda, Palinuridae) on cellular activity and growth was investigated through fluorometric quantification of nucleic acid levels. Late phyllosomata, post-settlement pueruli and juveniles were collected along the Western Australian coast between August and December 1992, by means of plankton nets and puerulus collectors. Early phyllosomata were obtained through laboratory rearing. Nucleic acid levels, as well as dry weights (DW), increased gradually during early phyllosomal stages; the RNA DNA ratio remained fairly constant between 0.3 and 0.5 units. During puerulus development, DNA levels (a measure for cellular growth) demonstrated a slight but insignificant increase; DW remained fairly constant. However, after ecdysis to the first juvenile stage, DNA levels were significantly higher (~ 0.93 mg DNA · individual −1), compared with early post-settlement pueruli (~0.35 mg DNA · ind. −1), and increased further during juvenile development (~ 1.08 mg DNA · ind. −1 in the second moult juvenile). DW of the second juvenile stage (142.5 mg) was approximately double that of the puerulus. RNA levels demonstrated a slight but insignificant decrease during puerulus development, and an increasing trend during juvenile development. RNA DNA ratios (an indicator for cellular activity) are high in the final phyllosoma (1.17 ± 0.13 units), and decrease significantly during the puerulus stage (to 0.49 ± 0.05 units in the early post-settlement puerulus) and first moult juveniles (0.26 ± 0.13 units), and only demonstrates a slight but insignificant recovery after the second moult juveniles (0.45 ±0.07 units). Water temperature appears to have an important impact on RNA levels, which approach zero immediately after ecdysis to the first juvenile stage when post-settlement pueruli were maintained at 23 °C; those maintained at 18 °C did not demonstrate a significant decrease. These observations are consistent with absence of feeding during the puerulus stage and further suggest that water temperature may have a substantial effect on puerulus development.

Effect of cadmium and ration level on oxygen consumption, RNA concentration and RNA-DNA ratio in two clones of Daphnia magna Straus

The rate of oxygen consumption, or respiration rate, of Daphnia magna is elevated as the food concentration of its environment increases, a phenomenon referred to as specific dynamic action (SDA). A possible cause of this response, the cost of tissue synthesis, was investigated using RNA concentration and RNA-DNA ratio as indices. The effects of cadmium on SDA was studied, to establish whether toxicants affect SDA either by increasing the rate of protein synthesis (for the repair/replacement of stress-damaged proteins), and/or by reducing feeding rate. Using two different genotypes, previously shown to differ in their sensitivities to cadmium, the possibility of genetic variation in response was also addressed.

Stimulation of in vivo pancreatic growth in the rat is mediated specifically by way of cholecystokinin-A receptors

Background/Aims: Cholecystokinin (CCK) and gastrin stimulate growth of rodent pancreas in vivo. However, it remains unclear whether these growth effects are mediated specifically by CCK-A receptors, CCK-B receptors, or both. To clarify this issue, the present study examined the effect of highly selective and biologically active CCK agonists on pancreatic growth. Methods: Rats were subcutaneously injected with either (1) CCK-8, a nonselective CCK agonist (2.50 μg/kg body wt); (2) A-71623, a selective CCK-A agonist, tert-butyl-oxycarbonyl-Trp-Lys (ε-N-2-methylphenylaminocarbonyl)-Asp-(N-methyl)-Phe-NH2 (1.84 μg/kg body wt); (3) SNF-8815; a selective CCK-B agonist, [(2R,3S)-β-MePhe28, N-MeNle31]CCK26–33 (2.40 μg/kg body wt); or (4) saline (control) for 21 days. Rats were killed, and pancreatic weight, protein content, RNA content, DNA content, protein-DNA ratio, RNA-DNA ratio, pancreatic area per nucleus, and number of mitoses per 10,000 acinar cells were determined. Results: Nonselective CCK agonist significantly increased pancreatic weight, protein, RNA, and DNA contents, and number of mitoses per 10,000 acinar cells. Likewise, selective CCK-A agonist significantly increased pancreatic weight, protein, RNA, and DNA contents, protein-DNA ratio, RNA-DNA ratio, pancreatic area per nucleus, and number of mitoses per 10,000 acinar cells. In contrast, selective and biologically active CCK-B agonist had no effect. Conclusion: These findings indicate that pancreatic growth is mediated specifically by CCK-A receptors in the rat in vivo.

Growth rates, nucleic acid concentrations, and [formula omitted] ratios of juvenile white shrimp, Penaeus vannamei boone, fed different algal diets

Macro- and microalgae are potentially important food resources for penaeid shrimp inhabiting coastal nursery grounds and aquaculture ponds. However, there are few data on the nutritional contribution of different algal species to juvenile shrimp growth. In this study, changes in whole body weight, RNA and DNA concentrations, and RNA DNA ratios of juvenile white shrimp, Penaeus vannamei Boone, fed different algal species were compared to assess the nutritional contribution of each species to shrimp growth. Shrimp fed a diatom culture composed primarily of Chaetoceros sp. were significantly heavier ( p < 0.05) than shrimp fed a monoculture of the green alga, Nannochloropsis oculata, fronds from the leafy macroalga, Ulva sp., or fronds from the filamentous macroalga, Enteromorpha sp. after 5 days. In addition, RNA/DNA ratios were significantly greater ( p 0 ̌ .05 ) in abdominal muscle tissue from diatom-fed shrimp. About 76% of the variation in shrimp growth rate could be explained by changes in RNA concentration, whereas RNA DNA ratio accounted for about 80% of the variation in growth rate. Diatoms can contribute substantially to short-term shrimp growth, and are probably important in coastal nursery grounds and aquaculture ponds when other food resources are scarce or to supplement available food.

Murine Cytomegalovirus Is Present in Both Chronic Active and Latent States in Persistently Infected Mice

Cytomegalovirus Induces serious disease in immunosuppressed individuals, often from an "activated" persistent infection. Whether the infection is chronically active or latent is unknown. Using murine cytomegalovirus (MCMV) in mice as a model system, we examined persistent infections in spleen, lung, and bone marrow of infected animals. At 28 days after infection, no virus could be recovered from any organs tested except salivary glands, and here, virus was cleared by 48 days. Virus could be retrieved at all times by cocultivation of spleen or lung with permissive cells. In addition, MCMV DNA was always present in spleen, lung, and bone marrow. After acute infection, RNA from the MCMV immediate early-1 (ie-1) gene was routinely found only in the lung. In spleen and bone marrow, only one sample from each organ examined at these times contained ie-1 RNA, and the RNA in these two samples was present at levels comparable to that found in acute infection. This suggests that the virus had reactivated. The ie-1 RNA found in the lung was present at a much lower RNA-DNA ratio than that found at early times. Taken together, these results indicate that persistent MCMV exists simultaneously in both chronic active and latent states.

RNA–DNA ratio of herring and sand lance larvae from Port Moller, Alaska: Comparison with prey concentration and temperature

ABSTRACTA key assumption of hypotheses that link the production of prey for larval fish with year‐class strength of fish is that larval growth and condition is food‐limited. We tested this assumption by comparing whole‐body RNA‐DNA ratios of individual Pacific herring, Clupea pallasi, larvae and Pacific sand lance, Ammodytes hex‐apterus, larvae from Port Moller, a subarctic Alaskan estuary, with prey concentration and temperature. RNA‐DNA ratios were correlated with larval length, but not with prey concentration or temperature. Ratios were not significantly different between a warm, well‐mixed station with low prey concentrations and a colder, stratified station with higher prey concentrations. Using RNA‐DNA ratios, we classified as starving 11 to 23% of first‐feeding (&lt; 13 mm long) herring larvae and 45% of first‐feeding (&lt; 7 mm long) sand lance larvae. However, starvation could not have been caused by low concentrations of prey because micro‐zooplankton prey concentrations were high enough (16 to 84 prey L_l) to support relatively high rates of growth. Therefore, starving larvae were either abnormal or they were stIII learning to forage. We conclude that the magnitude of starvation among first‐feeding herring and sand lance larvae, and, therefore, the total contribution of starvation to year‐class strength, is dependent not only on prey concentration, but on the proportion of a population of larvae that can feed effectively.

Comparison of Three Methods of Measuring RNA and DNA Concentrations of Individual Pacific Herring, Clupea pallasi, Larvae

Whole-body concentrations of RNA and DNA of individual Pacific herring, Clupea pallasi, larvae were measured with three methods that rely on the fluorescence of dyes bound to nucleic acids. Two methods use the dye ethidium bromide and do not purify nucleic acids, and one method uses ethidium bromide plus the DNA-specific dye bisbenzimidazole and purifies nucleic acids. Highly significant differences in RNA concentration and RNA–DNA ratios were found between the three methods. Significant differences in RNA concentration and RNA–DNA ratios were also found between yolk sac larvae and non-yolk sac larvae analyzed by one of the two ethidium bromide methods, with yolk sac larvae having the lowest ratios. These results suggest that compounds other than nucleic acids may interfere in the two ethidium bromide methods. Until a standard method for extraction and measurement of nucleic acids of larval fish is established, we recommend the use of techniques that purify nucleic acids.

Depletion of nutrient reserves during embryogenesis in the scallop Patinopecten yessoensis (Jay)

The levels of biochemical components and energy in spawned eggs of Patinopecten yessoensis (Jay) were higher and more consistent than those for other bivalve eggs which are cited in the literature. During embryogenesis, linear deposition of 0 to 40.5% dry wt of shell was the principal biochemical change. The energy calculated for shell deposition, 18.8 kJ·g −1, accounted for 74.4% of total energy depleted in the egg. Lipid, carbohydrate and protein were catabolized simultaneously and linearly with time of embryonic development. Total energy expended during development, 10.2 kJ·g −1, was derived 47.6% from lipid, 7.5% from carbohydrate and 44.9% from protein. Glucose was depleted linearly as the dominant source of carbohydrate energy in the egg. The RNA-DNA ratio, indicating rate of protein synthesis, declined exponentially from 11.98 in the fertilized egg to 1.91 in the D-larva. The combined saturated and monoethylenic fatty acids increased linearly with embryogenesis and the polyunsaturated fatty acids declined, principally in the linolenic family of acids. Eicosapentaenoic and docosahexaenoic acids exhibited, respectively, an energy and structural role during embryonic development. Protein and lipid were equally important as sources of energy during embryonic development of P. yessoensis.

Short- and long-term effects of ammonium chloride on RNA, DNA and protein concentrations in muscle and serum in the rainbow trout, Oncorhynchus mykiss

1. 1. Effects of ammonium-induced acidosis on white muscle RNA, DNA and protein concentrations were examined in the rainbow trout, Oncorhynchus mykiss. Serum protein concentrations were also determined. 2. 2. A single administration of ammonium chloride at a dose of sublethal level caused no changes in these parameters after 3 and 6 hr. 3. 3. Multiple administrations at a lesser dose caused significant decreases in RNA and serum protein concentrations 48 and 72 hr after the first administration. 4. 4. DNA and muscle protein concentrations remained unchanged throughout the experimental period. 5. 5. Significant decreases in RNA-DNA ratios and RNA-muscle protein ratios were primarily attributed to decreases in RNA concentrations.

Effects of tributyltin on survival, growth, morphometry, and RNA-DNA ratio of larval striped bass,Morone saxatilis

Effects of tributyltin (TBT) on survival, growth, morphometry, and RNA-DNA ratio in larval striped bass (Morone saxatilis) were assessed in three experiments. In Experiment I, 13 day old larvae were exposed to 0, 0.067, 0.766, or 2.284 micrograms TBT/L for 6 days. All larvae exposed to 2.284 micrograms/L died by day 5; exposure to 0.766 micrograms/L significantly reduced survival relative to controls (59.8% vs. 81.8%). Significant, concentration-dependent decreases in body depth occurred in larvae exposed to 0.067 and 0.766 micrograms/L. In Experiment II, all 16 day old larvae exposed to 1.498 micrograms/L died by day 6. Survival, weight, and morphometry parameters were not significantly different in larvae exposed to 0, 0.052, or 0.444 micrograms/L for 6 days. In Experiment III, survival was similar in 21 day old larvae exposed to 0, 0.055, 0.281, or 0.514 micrograms/L for 7 days. Notochord length and dry weight decreased significantly in larvae exposed to 0.514 micrograms/L. Weight and morphometry parameters were more sensitive indicators of sublethal stress than RNA-DNA ratio. Maximum TBT concentrations reported in Chesapeake Bay marinas are likely to cause increased larval mortality. Longer-term studies are needed to assess effects at less than 0.050 micrograms/L, which may be more representative of habitat conditions.

Effects of nickel chloride on lactating rats and their suckling pups, and the transfer of nickel through rat milk

The excretion of nickel into rat milk following subcutaneous (sc) doses of nickel chloride (NiCl 2) and the effects on the lactating rat and her suckling pups were determined. Plasma and milk Ni concentrations increased in a dose-dependent manner 4 hr after single doses of 0, 10, 50, or 100 μmol NiCl 2/kg to lactating rats, giving milk/plasma Ni ratios of 0.02. Peak plasma Ni concentrations were reached 4 hr after injection, while milk Ni increased until 12 hr and remained elevated at 24 hr. Dosing for 4 days at 50 or 100 μmol NiCl 2/kg/day led to higher milk/plasma Ni ratios of 0.10. These doses of NiCl 2 had no effect on body weight but caused decreased food consumption, thymic atrophy, and a small increase in hepatic lipid peroxidation in the dams. Significant alterations in milk composition, which were not due to decreased food consumption as determined in pair-fed rats, included increased milk solids (42%) and lipid (110%), and decreased milk protein (29%) and lactose (61%). NiCl 2 treatment also caused significant decreases in mammary RNA content and the RNA DNA ratio compared to both ad libitum-fed and pair-fed rats, indicating that milk synthetic activity was reduced by NiCl 2. Pups suckling the NiCl 2-treated dams had plasma Ni concentrations of 24 and 48 μg/liter in the 50 and 100 μmol/kg dose groups, respectively, and had decreased liver weight but no changes in hepatic lipid peroxidation or thymus weight. The results indicate that high doses of NiCl 2 led to the excretion of Ni into rat milk and changes in milk quality and production. Reductions in liver weight in the suckling pups were also observed which may have been due to nickel exposure or to changes in milk composition.

Differential effects of triiodothyronine on rat left and right ventricular function and the influence of metoprolol

The influence of triiodothyronine (T3) on right ventricular functional parameters was tested and compared to the alterations induced in the left ventricle. Female Sprague-Dawley rats received daily injections of T3 (0.2 mg/kg s.c.) for 3 days and a constant i.v. infusion of 0.9% NaCl or the β 1-receptor blocker metoprolol (1 mg/kg/h). The hyperthyroid state after 3 days administration of T3 was characterized by an increase in heart rate and cardiac output and a decrease in the systemic peripheral resistance. However, pulmonary vascular resistance was unchanged. β-Receptor blockade reduced heart rate to the control level without affecting the elevation in cardiac output. The T3 group showed a marked increase in right ventricular systolic pressure (RVSP) and mean pulmonary artery pressure, whereas left ventricular systolic pressure (LVSP) and mean aortic pressure were not significantly changed. Metoprolol had no effect on LVSP, and attenuated the increase in RVSP. Furthermore, T3 induced a considerable increase in dP dt max in both ventricles, which was reduced nearly to control level by concomitant metoprolol infusion. The T3-induced percentage weight gain of the right ventricular free wall (RV) was more pronounced than that of the left ventricle (LV) as indicated by the significant increase in the RV LV weight and the RNA DNA ratios. Metoprolol did not affect significantly the T3-induced left and right ventricular hypertrophy, but attenuated slightly the elevated RV LV weight ratio. Our results indicate a different action of T3 on systemic and pulmonary circulation.

RNA, DNA and protein during early development in feeding and starved cod ( Gadus morhua L.) larvae

Quantitative changes in DNA, RNA and soluble protein were studied in the early stages of developing cod larvae. Similar macromolecular metabolism was observed in larvae reared under different conditions in laboratory tanks and a saltwater pond. In response to feeding, both groups exhibited high RNA production and elevated RNA DNA ratios but the response of the pond larvae was greater and more rapid. Starved larvae were characterized by higher amounts of total DNA compared with fed larvae, and laboratory fed larvae had a higher total DNA than pond larvae. A common observation for all fed larvae was a sharp increase followed by a decrease in total DNA between the end of the yolk sac period and the time of mass death. The most pronounced difference between starving and feeding larvae was seen in their RNA content.

Ontogenetic Development of Growth Rates in Larval Pacific Herrings, Clupea harengus pallasi, Measured with RNA–DNA Ratios in the Strait of Georgia, British Columbia

During the spring of 1986, a cohort of Pacific herring, Clupea harengus pallasi, larvae was sampled for 36 d in the Strait of Georgia to measure growth rates using RNA–DNA ratios for individual larvae. Concurrent with the field study, a population of herring larvae was starved from hatching in captivity for comparison with those caught in the field. The mean RNA–DNA ratio at hatching for the starved larvae was close to 2 but it quickly rose to 3.4 by age 4 d. The mean RNA–DNA ratio subsequently dropped back to 2 and below by age 8 d, presumably reflecting the exhaustion of the endogenous food supply of the yolk sac. The mean RNA–DNA ratio at the calculated point-of-no-return was 2.06 which was very similar to the zero protein growth rate or what we define as the "critical ratio." Herring larvae from the field generally showed an increase in the RNA–DNA ratio over the 36 d from approximately 2 to 7 although the first 18 d showed more variation than the latter. There was no evidence of mass starvation ("critical period") for the 1986 year class but there was a noticeable drop in the growth rate during the change to exogenous feeding. We suggest that starvation probably only directly affected the developing larvae during a window of about 11 d. Frequency distributions of the RNA–DNA ratios are shown for larvae over time.

Changes in the levels of nucleic acid, protein, total free amino acid and glycogen, and activity of acid phosphatase in the eggs, during normal embryonic development of the rice moth, Corcyra cephalonica, stainton (Lepidoptera: Pyralidae)

DNA, RNA, protein, total free amino acid and glycogen levels, and acid phosphatase activity were determined in the eggs of the rice moth, Corcyra cephalonica during normal embryonic development. The DNA levels remain lower and relatively constant in the eggs of 6, 12 and 24 h of age, while in the eggs of older age groups, i.e. 36, 48, 60 and 72 h, a marked increase in the DNA levels occurs. The RNA content shows a significant rise up to the 36 h stage, then its level declines sharply. The RNA DNA ratio increases markedly from the 6 h stage and reaches to its maximum in the eggs at the 36 h stage, indicating increase in the degree of synthetic activity that takes place during such period of embryonic development. In the later phases this ratio declines rapidly and reaches to a minimum level in the eggs of 72 h of age. The level of protein is highest while that of total free amino acid is lowest in the eggs of 6 h of age. In the 12-h-old eggs, the protein level declines markedly with a rapid increase in total free amino acid concentration. Periods beyond the 12 h stage are represented by slight fluctuations in the amount of both these constituents. The age-related rise and fall in glycogen levels are similar to that of RNA. The activity of acid phosphatase is minimum in the 6-h-old eggs and reaches to a peak level in the eggs of 72 h of age following a sigmoid pattern.