Changes In RNA Content Research Articles

THE INFLUENCE OF ACUTE CEREBRAL BLOOD CIRCULATION DISORDERS IN THE POOL OF CAROTID ARTERIES ON THE RNA CONTENT IN THE CELLS OF THE LYMPHOID POPULATION OF THE RATS’ THYMUS OF DIFFERENT AGE GROUPS

The aim of the work – to find out the age-related features of the response of RNA cells ofthe lymphoid population of the thymus to an acute disturbance of cerebral blood flow inthe pool of carotid arteries in six- and nine-month-old rats.Materials and methods. Acute cerebrovascular accident was simulated in 6- and9-month-old white non-linear laboratory rats by bilateral carotid artery clamping for 20min. followed by reperfusion. The thymus was taken on the 12th day of the postischemicperiod, fixed in Buen’s solution, after standard histological processing it was embedded inparaffin, and serial sections with a thickness of 5 μm were made. After deparaffinization,rehydration, and staining with hallocyanine- chromium alum according to Einarson,histological sections were analyzed in a digital image analysis system VIDAS-386(Kontron Electronik, Germany) with a fluorescent microscope AXIOSKOP (Zeiss,Germany). Total RNA content was expressed in units of optical density (EOP per 1 mm2). The results. In the cells of the lymphoid population of all structural and functional zones ofthe thymus of control rats of both age groups, an increase in RNA content was establishedin the direction from immature to more mature classes (p<0.05). This regularity persistsin the post-ischemic period. In the cells of the lymphoid population of the subcapsular anddeep cortical zones of the thymus, the RNA content significantly prevails in six-month-oldrats, in intralobular perivascular spaces – in nine-month-old rats, and in the medullaryzone there are no age differences. Postischemic changes in RNA content in six-month-oldrats in the subcapsular zone and intralobular perivascular spaces of the thymus consistin its decrease in immature cell classes and its increase in mature small thymocytes(р<0.05); in the deep cortex – in growth in all classes of thymocytes (p<0.05). In ninemonth-old animals, the differences were in the increase in RNA content in the subcapsularzone and in less mature middle thymocytes, in the deep cortex – in a decrease in RNAcontent in all classes, except small thymocytes, in intralobular perivascular spaces – ina decrease in RNA content in all classes of thymocytes (p<0.05 for all cases). In themedullary zone of animals of both age groups, changes are unidirectional (decrease inRNA content, p<0.05).Conclusion. Age differences in the nature of postischemic changes in the content of RNAin thymocytes are present in all structural and functional zones of the gland, with theexception of the medullary, in which the changes were unidirectional in both age groups.

Age features of the thymocite RNA response in the thymus structural and functional areas to blood circulation disorders in the pool of carotic arteries in rats

Introduction. Ischemic-reperfusion injuries of the brain are accompanied by immunological disorders, which in their turn can extend post-ischemic changes in the brain. The studies of structural and functional changes in the thymus cells caused byischemia-reperfusion of the brain can supplement the existing understanding of the mechanism of the above interaction.
 The aim of the study. To investigate the reaction of thymocyte RNA in the structural and functional areas of the thymus gland to blood circulation disturbances in the carotid artery pool.
 Results. In rats of both age groups, cerebral ischemia-reperfusion reduces the content of RNA in the thymus cells in all the structural and functional areas of the thymus except the deep cortical one in one-month rats and the sub-capsular one in three-month rats. 
 Conclusions. Acute circulatory disorders in the pool of the carotid arteries result in certain changes in RNA content in all the structural and functional areas of the thymus with age-related and structural features available.

Вплив 2-(3-аліл-4-оксо-3,4-дигідро-хіназолін- 2-іл-сульфоніл)-N-(2,6-дихлорфеніл)-цераміду на складові хроматину та стан антиоксидантної системи в саркомі 45 і незмінених тканинах шкіри щурів

Стрімке поширення онкологічних захворювань у ХХІ столітті в усьому світі зумовлює інтенсифікацію хіміотерапевтичного лікування даної патології зі застосуванням усе нових і нових цитотоксичних і цитостатичних агентів. Однак це зумовлює зростання й числа побічних ефектів і небажаних наслідків використання даних препаратів. Неспецифічна дія щодо всього організму пацієнта та висока токсичність даної групи лікарських засобів, зокрема, їхня кардіо-, нефро- та нейротоксичність, а також відсутність достатньої інформації щодо віддалених наслідків введення протипухлинних засобів на стан прилеглих тканин, які не були захоплені інвазією пухлини, зумовлюють нагальну потребу в системному вивченні біохімічних змін не лише в пухлині, але й поза її межами. У попередніх експериментах нами було проведене вивчення впливу протипухлинного похідного хіназоліну на складові хроматину, процеси фрагментації ДНК, вміст небілкових і пов’язаних з білками SH-груп у карциномі Герена та незмінених тканинах матки й виявлено специфічність його впливу на низку показників виключно в тканині пухлини. У зв’язку з цим актуальним є з’ясування, чи є виявлена специфічність похідного хіназоліну характерною лише для тканини матки, чи вона поширюється й на інші тканини організму. Мета дослідження – вивчити вплив 2-(3-аліл-4-оксо-3,4-дигідро-хіназолін-2-іл-сульфоніл)-N(2,6-дихлорфеніл)-цераміду (АХДЦ) на ДНК, РНК, білки хроматину, процеси фрагментації ДНК, вміст небілкових і пов’язаних з білками SH-груп у саркомі 45 і незмінених тканинах шкіри щурів. Тварини були розподілені на 3 групи по 6 тварин у кожній: 1 – інтактні щури; 2 – негативний контроль (саркома 45); 3 – саркома 45 + АХДЦ (29,93 мг/кг). Вивчення впливу АХДЦ на ДНК, РНК, білки хроматину, процеси фрагментації ДНК, вміст небілкових і пов’язаних з білками SH-груп у саркомі 45 і незмінених тканинах шкіри показало, що дана сполука вірогідно змінювала більшість досліджуваних показників як порівняно з інтактними тваринами, так і з саркомою 45 без лікування. Специфічність впливу АХДЦ на клітини пухлин була найвираженішою щодо ДНК-фрагментації та змін вмісту РНК, співвідношень РНК/ДНК і РНК/НК. Щодо впливу на вміст SH-груп у тканині саркоми 45 і неуражених пухлиною тканинах шкіри, то в даному випадку ефект АХДЦ був протилежним за напрямком стосовно змін вмісту небілкових і пов’язаних з білками SH-груп.

From the Literature

From the Literature

Total Cellular RNA Modulates Protein Activity.

RNA constitutes up to 20% of a cell's dry weight, corresponding to ∼20 mg/mL. This high concentration of RNA facilitates low-affinity protein-RNA quinary interactions, which may play an important role in facilitating and regulating biological processes. In the yeast Pichia pastoris, the level of ubiquitin-RNA colocalization increases when cells are grown in the presence of dextrose and methanol instead of methanol as the sole carbon source. Total RNA isolated from cells grown in methanol increases β-galactosidase activity relative to that seen with RNA isolated from cells grown in the presence of dextrose and methanol. Because the total cellular RNA content changes with growth medium, protein-RNA quinary interactions can alter in-cell protein biochemistry and may play an important role in cell adaptation, critical to many physiological and pathological states.

Next generation of cardiovascular studies: transcriptional responses of the human myocardium during cardiac surgery.

Next generation of cardiovascular studies: transcriptional responses of the human myocardium during cardiac surgery.

Changes in prion replication environment cause prion strain mutation

Interspecies prion transmission often leads to stable changes in physical and biological features of prion strains, a phenomenon referred to as a strain mutation. It remains unknown whether changes in the replication environment in the absence of changes in PrP primary structure can be a source of strain mutations. To approach this question, RNA content was altered in the course of amplification of hamster strains in serial protein misfolding cyclic amplification (sPMCAb). On adaptation to an RNA-depleted environment and then readaptation to an environment containing RNA, strain 263K gave rise to a novel PrP(Sc) conformation referred to as 263K(R+), which is characterized by very low conformational stability, high sensitivity to proteolytic digestion, and a replication rate of 10(6)-fold/PMCAb round, which exceeded that of 263K by almost 10(4)-fold. A series of PMCAb experiments revealed that 263K(R+) was lacking in brain-derived 263K material, but emerged de novo as a result of changes in RNA content. A similar transformation was also observed for strain Hyper, suggesting that this phenomenon was not limited to 263K. The current work demonstrates that dramatic PrP(Sc) transformations can be induced by changes in the prion replication environment and without changes in PrP primary structure.

Effects of indoxacarb on total protein, RNA, and DNA contents in the ovaries and fat bodies of Nilaparvata lugens Stål (Hemiptera: Delphacidae) adult females

The new insecticide indoxacarb was recently developed with high insecticidal activity in the control of lepidopteran pests, and recent findings demonstrated that indoxacarb also significantly suppressed the fecundity of Nilaparvata lugens Stål (Hemiptera: Delphacidae) populations, a serious insect pest of rice in Asia. The current study investigated the total protein, RNA, and DNA contents in the ovaries and fat bodies of N. lugens adult females after treatment with the insecticide indoxacarb. The results demonstrated that all of the tested concentrations of indoxacarb caused a significant decrease in the protein and RNA contents in the ovaries and fat bodies of the adult females that developed from nymphs fed indoxacarb-treated rice plants compared with those from nymphs fed untreated rice plants, while the DNA contents did not significantly decrease except at 5days among all of the tested days after emergence. In general, the protein and RNA contents in both the ovaries and the fat bodies decreased linearly with the concentration of indoxacarb applied. There was a significant negative correlation between the total protein and RNA contents and the concentrations of indoxacarb, showing that the total protein and RNA were more sensitive to indoxacarb than was the DNA, and that the changes in RNA contents in turn influence protein synthesis in both the ovaries and fat bodies. The RNA-to-protein ratios in both the ovaries and fat bodies were consistently 0.2 in all of the treatment groups and in the control groups.

A simple analytical and experimental procedure for selection of reference genes for reverse-transcription quantitative PCR normalization data

Variation in cellular activity in a tissue induces changes in RNA concentration, which affects the validity of gene mRNA abundance analyzed by reverse transcription quantitative PCR (RT-qPCR). A common way of accounting for such variation consists of the use of reference genes for normalization. Programs such as geNorm may be used to select suitable reference genes, although a large set of genes that are not co-regulated must be analyzed to obtain accurate results. The objective of this study was to propose an alternative experimental and analytical protocol to assess the invariance of reference genes in porcine mammary tissue using mammary RNA and DNA concentrations as correction factors. Mammary glands were biopsied from 4 sows on d 110 of gestation (prepartum), on d 5 (early) and 17 (peak) of lactation, and on d 5 after weaning (postweaning). Relative expression of 7 potential reference genes, API5, MRPL39, VAPB, ACTB, GAPDH, RPS23, and MTG1, and one candidate gene, SLC7A1, was quantified by RT-qPCR using a relative standard curve approach. Variation in gene expression levels, measured as cycles to threshold at each stage of mammary physiological activity, was tested using a linear mixed model fitting RNA and DNA concentrations as covariates. Results were compared with those obtained with geNorm analysis, and genes selected by each method were used to normalize SLC7A1. Quantified relative mRNA abundance of GAPDH and MRPL39 remained unchanged across stages of mammary physiological activity after accounting for changes in tissue RNA and DNA concentration. In contrast, geNorm analysis selected MTG1, MRPL39, and VAPB as the best reference genes. However, when target gene SLC7A1 was normalized with genes selected either based on our proposed protocol or by geNorm, fold changes in mRNA abundance did not differ. In conclusion, the proposed analytical protocol assesses expression invariance of potential reference genes by accounting for variation in tissue RNA and DNA concentrations and thus represents an alternative method to select suitable reference genes for RT-qPCR analysis.

Conventional apoptosis assays using propidium iodide generate a significant number of false positives that prevent accurate assessment of cell death

The advent of flow cytometry-based applications has significantly impacted the study of cellular apoptosis. Propidium iodide (PI) is a commonly used viability stain in these studies. Unfortunately, we find that conventional Annexin V/PI protocols lead to a significant number of false positive events (up to 40%), which are associated with PI staining of RNA within the cytoplasmic compartment. Both primary cells and cell lines are affected, with large cells (nuclear: cytoplasmic ratios <0.5) showing the highest occurrence. This distribution spans a wide range of animal models including mice, swine, avian, and teleost fish and potentially affects up to 1016 out of 1019 of peer-reviewed papers published in this area since 1995. We show that the primary ramifications from these findings relate to cells experiencing changes in RNA content. Virally infected cells, for example, are qualified as undergoing apoptosis in response to infection based on conventional staining protocols; in fact, these cells are alive and actively producing viral RNA that can serve to produce additional infectious viral particles. Based on our observations we propose a modified protocol, show that it overcomes previous drawbacks for this technique, and that it will allow for more accurate assessment of cell death across various platforms.

Insecticide-Induced Changes in Protein, RNA, and DNA Contents in Ovary and Fat Body of Female &lt;I&gt;Nilaparvata lugens&lt;/I&gt; (Hemiptera: Delphacidae)

The widespread use of insecticides is known to cause resurgence in Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) populations, a serious insect pest of rice, Orzya sativa L., crops in Asia. The current study investigated insecticide-induced changes in protein, RNA, and DNA levels in the ovary and fat body of adult female N. lugens. Potted rice plants were sprayed with different concentrations of imidacloprid, triazophos, and detamethrin. The results showed that all three insecticides caused a significant increase in protein and RNA contents in the ovary and fat body of adult females developed from nymphs fed on treated plants compared with those from on untreated plants, although there was no significant effect on DNA content. In general, protein and RNA contents in both ovary and fat body increased linearly with insecticide concentrations or days after emergence (DAEs) when they were applied. There was a significant correlation between protein content and RNA content in both ovary and fat body. In addition, the relationship between ratios of RNA to protein in ovary and fat body of adult female N. lugens and insecticide concentrations showed a significant positive correlation for most DAEs of imidacloprid and several DAEs of triazophos and deltamethrin treatments. These findings suggest that RNA in both ovary and fat body was more sensitive to insecticides and that the insecticide-induced changes in RNA content in turn influence protein synthesis in ovary and fat body. Consistently, RNA-to-protein ratios in ovary and fat body were approximately 0.42 in all treatments and controls.

Skeletal muscle hypertrophic effect of clenbuterol is additive to the hypertrophic effect of myostatin suppression

It is well established that myostatin (MSTN) suppression or clenbuterol (CL) administration enhances skeletal muscle mass, but the interaction of MSTN suppression and CL administration on skeletal muscle mass has not been examined. To examine the interaction of MSTN suppression and CL administration on skeletal muscle mass, 35 days old female wild type and heterozygous MSTN‐pro transgenic mice that exhibits 20‐30 % enhanced muscle mass by overexpression of MSTN prodomain were administrated 0 and 20 ppm CL in drinking water for 2 wks. Four different muscle samples from hind legs were collected at 1 wk and 2 wk after CL administration. Regardless of genotype, CL significantly increased the body and muscle mass at 1 wk or 2 wk after CL administration. No significant genotype and CL interactions on body and muscle mass were observed. DNA concentration of plantaris muscle was significantly decreased by CL administration for 1 wk or 2 wk regardless of genotype. RNA concentration of plantaris muscle was significantly increased by CL administration for 1 wk in both genotypes, but no significant change in RNA concentration was observed at 2 wk of CL administration in both genotypes. The RNA/DNA ratio in plantaris muscle was significantly elevated by CL administration for 1 wk or 2 wk in both genotypes. In summary, the result of this study demonstrates that skeletal muscle hypertrophic effect of CL is additive to the hypertrophic effect of MSTN suppression, suggest that the mechanism of action of CL leading to skeletal muscle hypertrophy might be different from that of MSTN.

Modeling Neisseria meningitidis B metabolism at different specific growth rates

Neisseria meningitidis is a human pathogen that can infect diverse sites within the human host. The major diseases caused by N. meningitidis are responsible for death and disability, especially in young infants. At the Netherlands Vaccine Institute (NVI) a vaccine against serogroup B organisms is currently being developed. This study describes the influence of the growth rate of N. meningitidis on its macro-molecular composition and its metabolic activity and was determined in chemostat cultures. In the applied range of growth rates, no significant changes in RNA content and protein content with growth rate were observed in N. meningitidis. The DNA content in N. meningitidis was somewhat higher at the highest applied growth rate. The phospholipid and lipopolysaccharide content in N. meningitidis changed with growth rate but no specific trends were observed. The cellular fatty acid composition and the amino acid composition did not change significantly with growth rate. Additionally, it was found that the PorA content in outer membrane vesicles was significantly lower at the highest growth rate. The metabolic fluxes at various growth rates were calculated using flux balance analysis. Errors in fluxes were calculated using Monte Carlo Simulation and the reliability of the calculated flux distribution could be indicated, which has not been reported for this type of analysis. The yield of biomass on substrate (Y(x/s)) and the maintenance coefficient (m(s)) were determined as 0.44 (+/-0.04) g g(-1) and 0.04 (+/-0.02) g g(-1) h(-1), respectively. The growth associated energy requirement (Y(x/ATP)) and the non-growth associated ATP requirement for maintenance (m(ATP)) were estimated as 0.13 (+/-0.04) mol mol(-1) and 0.43 (+/-0.14) mol mol(-1) h(-1), respectively. It was found that the split ratio between the Entner-Doudoroff and the pentose phosphate pathway, the sole glucose utilizing pathways in N. meningitidis, had a minor effect on ATP formation rate but a major effect on the fluxes going through for instance the citric-acid cycle. For this reason, we presented flux ranges for underdetermined parts of metabolic network rather than presenting single flux values, which is more commonly done in literature.

A novel sequence-specific RNA quantification method using nicking endonuclease, dual-labeled fluorescent DNA probe, and conformation-interchangeable oligo-DNA

We have developed a novel, single-step, isothermal, signal-amplified, and sequence-specific RNA quantification method (L-assay). The L-assay consists of nicking endonuclease, a dual-labeled fluorescent DNA probe (DL-probe), and conformation-interchangeable oligo-DNA (L-DNA). This signal-amplified assay can quantify target RNA concentration in a sequence-specific manner with a coefficient of variation (Cv) of 5% and a lower limit of detection of 0.1 nM. Moreover, this assay allows quantification of target RNA even in the presence of a several thousandfold excess by weight of cellular RNA. In addition, this assay can be used to measure the changes in RNA concentration in real-time and to quantify short RNAs (<30 nucleotides). The L-assay requires only incubation under isothermal conditions, is inexpensive, and is expected to be useful for basic research requiring high-accuracy, easy-to-use RNA quantification, and real-time quantification.

Kinetic Analysis of the Entire RNA Amplification Process by Qβ Replicase

The kinetics of the RNA replication reaction by Qbeta replicase were investigated. Qbeta replicase is an RNA-dependent RNA polymerase responsible for replicating the RNA genome of coliphage Qbeta and plays a key role in the life cycle of the Qbeta phage. Although the RNA replication reaction using this enzyme has long been studied, a kinetic model that can describe the entire RNA amplification process has yet to be determined. In this study, we propose a kinetic model that is able to account for the entire RNA amplification process. The key to our proposed kinetic model is the consideration of nonproductive binding (i.e. binding of an enzyme to the RNA where the enzyme cannot initiate the reaction). By considering nonproductive binding and the notable enzyme inactivation we observed, the previous observations that remained unresolved could also be explained. Moreover, based on the kinetic model and the experimental results, we determined rate and equilibrium constants using template RNAs of various lengths. The proposed model and the obtained constants provide important information both for understanding the basis of Qbeta phage amplification and the applications using Qbeta replicase.

Age‐dependent decreases in mitogen‐stimulation level and RNA content in peripheral blood mononuclear cells of down syndrome patients

The aim of the present study was to determine whether or not the phytohemagglutinin (PHA)-activated proliferation and average RNA content in peripheral blood mononuclear cells (PBMC) of Down syndrome (DS) patients change with age. Stimulated portion of PBMC and total RNA levels in these cells after 72 h of PHA stimulation from 38 DS patients were compared with 28 age-matched healthy controls using flow cytometric measurement. Decreased ratio of PBMC from DS patients undergoes mitogenic stimulation with age (r = -0.84, P = 0.000). This decrease is not observed in the cells of control individuals (r = 0.03, P = 0.869). Stimulated PBMC in infants with DS have higher level of RNA contents compared to controls (Z = 2.227, P = 0.026). While RNA content in mitogen-stimulated PBMC of DS decreased progressively and significantly with age (r = -0.70, P = 0.000), no significant age-related change in RNA content was found among the cells of healthy individuals in the range of 0-27 year old (r = 0.275, P = 0.157, P > 0.05). Age-dependent decreases in mitogen-activated proliferation ratio and average RNA content of PBMC from DS patients appear as regular events. These results may contribute to the explanation of the immune deficiency seen in DS patients since the PHA-stimulated cells are principally T-lymphocytes. This is the first report on the decrease in PHA-stimulated proliferation ratio (stimulability) and RNA level in PBMC of DS patients in relation to age.

Ribonucleases during ripening and after-ripening in Triticum durum embryos

Summary Total and polyadenylated RNA content changes during ripening and after-ripening in embryos of Triticum durum cv. Cappelli. In this work, RNase activity was studied by means of enzymatic assays and activity staining SDS-PAGE in embryos at different stages of maturation and after-ripening. Qualitative and quantitative changes of RNases were found. Of particular interest was the continuous presence of acidic RNase in embryos, and the disappearance of neutral RNase activities during after ripening. Salt-inhibited RNases disappeared 42 days after anthesis, while salt-stimulated RNases with higher mobility disappeared in fully ripened embryos. Salt-stimulated RNases with lower mobility disappeared during after-ripening. The disappearance of neutral RNase activities during ripening may be related to the different physiological status induced by dehydration.

Nucleic acid concentrations (DNA, RNA) in the continental and deep-sea sediments of the eastern Mediterranean: relationships with seasonally varying organic inputs and bacterial dynamics

In order to study temporal variations of the genetic material in the continental shelf and deep-sea sediments of the extremely oligotrophic Cretan Sea, samples were collected on seasonal basis from August 1994 to September 1995, with a multiple corer, at seven stations (from 40 to 1540 m depth). Surface sediments (0–1 cm) were sub-sampled and analyzed for nucleic acid content (DNA, RNA) and bacterial density. DNA concentrations in the sediments were high (on annual average, 25.0 μg g -1) and declined with increasing water depth, ranging from 3.5 to 55.2 μg g -1. DNA concentrations displayed wide temporal changes also at bathyal depths confirming the recent view of the large variability of the deep-sea environments. Also RNA concentrations decreased with increasing water depth (range: 0.4–29.9 μg g -1). The ratio of RNA to DNA did not show a clear spatial pattern but was characterized by significant changes between sampling periods. DNA concentrations were significantly correlated with protein and phytopigment concentrations in the sediment, indicating a possible relationship with the inputs of primary organic matter from the photic layer. Bacterial densities were generally high (range: 0.9–4.6×10 8 cells g -1) compared to other deep-sea environments and decreased with increasing water depth. Estimates of the bacterial contribution to the sedimentary genetic material indicated that bacterial-DNA accounted, on annual average, for a small fraction of the total DNA pool (4.3%) but that bacterial-RNA represented a significant fraction of the total sedimentary RNA (26%). Bacterial contribution to nucleic acids increased, even though irregularly, with increasing depth. In deep-sea sediments, changes in RNA concentrations appear to be largely dependent upon bacterial dynamics. Estimates of the overall living contribution to the DNA pools (i.e. microbial plus meiofaunal DNA) indicated that the large majority (about 90%) of the DNA in continental and deep-sea sediments of the eastern Mediterranean was detrital. The non-living DNA pools reach extremely high concentrations up to 0.41 g DNA m -2 cm -1. Thus, especially in deep benthic habitats, characterized by low inputs of labile organic compounds, detrital DNA could represent a suitable and high quality food source or a significant reservoir of nucleic acid precursors for benthic metabolism.

Estimation of starvation and diel variation of the RNA/DNA ratios in field-caught Sardina pilchardus larvae off the north of Spain

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 164:273-283 (1998) - doi:10.3354/meps164273 Estimation of starvation and diel variation of the RNA/DNA ratios in field-caught Sardina pilchardus larvae off the north of Spain M. Alexandra Chícharo1,*, Luis Chícharo1, Luis Valdés2, Eduardo López-Jamar3, Pedro Ré4 1UCTRA, Universidade do Algarve, Campus de Gambelas, P-8000 Faro, Portugal 2Instituto Español de Oceanografia, Promontorio de San Martín, s/n, E-39004 Santander, Spain 3Instituto Español de Oceanografia, Avda. De Brasil, 31, E-28020 Madrid, Spain 4Lab. Mar. Guia, Fac. Ciências da Universidade de Lisboa, Est. do Guinelio, P-2750 Cascais, Portugal *E-mail: mchicharo@ualg.pt The aim of this study was to analyse the general larval condition, to determine the incidence of starvation and to investigate the effect of time of day on RNA/DNA ratios among field-caught Sardina pilchardus (L.) larvae. The larvae were collected during 4 research cruises off northern Spain, during March, April, May and June 1992. A highly sensitive fluorometric method for nucleic acid quantification was applied to larvae of S. pilchardus. The means of the RNA/DNA ratio were relatively high, so the larvae collected off northern Spain were generally in good condition. Low percentages of starving larvae (RNA/DNA ratio less than 1.3), ranging from 0 to 3.23%, were found over the 4 mo. The RNA/DNA ratios were significantly correlated with zooplankton biomass. Larvae collected at night revealed higher RNA/DNA ratios compared to larvae caught during the day. This seems to indicate that there is some endogenous rhythm in the production of RNA. It would then follow that, if there are diel changes in RNA concentrations, average RNA indices can be unrepresentative if there is any day/night bias in sampling. Fish larvae · RNA/DNA · Sardina pilchardus · Starvation · Diel variation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 164. Publication date: April 09, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Effect of temporary reductions in feeding on protein synthesis and energy storage of juvenile Atlantic salmon

Biochemical and tissue‐composition indices were used to determine the impacts of temporary feeding reductions on juvenile Atlantic salmon (4.2g initial weight). Three levels of food reduction (fasting, 20% of control, 50% of control) lasting for 2, 4 or 8 days were compared to a control group (constant feeding at 2.75% of body weight day−1). Ornithine decarboxylase (ODC) activity and RNA concentrations were used to measure changes in protein synthesis; condition factor (K), liver‐somatic index (LSI), visceral‐somatic index (VSI), and gut index (GI)were used to provide information on stored energy levels. Results showed that physiological adjustments to decreases or increases in feeding occur very quickly. The most rapid responses were changes in ODC activity (within 2 days) and LSI (2–4 days). Changes in RNA concentrations and K required 4–8 days. There was no apparent effect of the treatments on VSI or GI. Temporary reductions of feeding lasting 2 days or less would not be detected by any index except ODC activity. Changes in the indices are discussed with respect to short‐term changes in rates of protein synthesis and energy storage.