Temperature induced metabolic costs in carp, Cyprinus carpio L., during warm and cold acclimatization

The oxygen consumption of 6 carps was measured in a flow-through respirometer when water temperature was reduced from 23 to 7°C and increased from 23 to 33°C as well as from 11 to 32°C. The metabolic reaction of Cyprinus carpio L. was assessed at 3 levels: standard, routine and spontaneous. The Standard Metabolic Rate increased and the Q₁₀ decreased with rising temperatures. A quadratic relation was established between metabolic rates and temperature level. The enery exenditure above Standard Metabolic Rate induced by temperature changes was 6.65 ± 1.97 kJ kg^-0.8 d^-1 (x ± S.E., N = 6).
Costs for temperature acclimatization amounted to 29 %, 24 % and 9 % of the energy required for standard, routine and spontaneous action metabolism, respectively.

Zusammenfassung

Temperaturinduzierte Stoffwechselerhöhungen bei Karpfen , Cyprinus carpio L., während Warm- und Kaltakklimatisierung
Wir haben untersucht, wie der Stoffwechsel von Cyprinus carpio im Standard-, Routine- und Spontanniveau während einer Kalt- und Warmakklimatisierung im Bereich von 7–33 °C reagiert. Dieses Verhalten wurde mit Hilfe eines Durchfluß-Respirometers ermittelt. Die "Standard Metabolic Rate" nahm zu und der Q₁₀ verringerte sich mit steigender Temeratur.
Eine quadratische Beziehung besteht zwischen den Stoffwechselraten und dem Temperaturniveau. Die durch Temperaturänderun induzierte Stoffwechselerhöhung über die Standardrate wurde für den Meßbereich mit 6.65 ± 1.97 kJ kg^-0.8 d^-1 (x ± S.E., N = 6) ermittelt.
Der Anteil temperaturinduzierter Aufwendungen entsprach 29%, 24% und 9% des Standard-, Routine- und Spontanverbrauches an Energie.     

Metabolic fractionation of stable carbon isotopes: implications of different proximate compositions for studies of the aquatic food webs using δ13C data

In two laboratory experiments using tilapia (Oreochromis niloticus) and common carp (Cyprinus carpio), we investigated the effect of lipid content in the fish carcass on the stable carbon isotope ratio (δ¹³C). In both experiments, a significant negative correlation was found between lipid content in the carcass dry matter and δ¹³C of total dry matter, but there was no influence on the δ¹³C of fat-free dry matter or lipids. As the lipid content of fish is known to vary with reproductive stage, season or nutritional state, separate analysis of fractions of the proximate composition of dry matter will lead to more reliable results than analysing the whole body. The differences in δ¹³C between diet and fish carcass (trophic shift) were different for the two species, calling for feeding trials under controlled conditions using the species and the feeds in question before applying the stable isotope tracer technique in the analysis of food webs. Received: 1 December 1997 / Accepted: 1 March 1998     

Uncoupling of the dynamics of host–pathogen interaction uncovers new mechanisms of viral interferon antagonism at the single-cell level

Antiviral defence in mammals is mediated through type-I interferons (IFNs). Viruses antagonise this process through expression of IFN antagonist proteins (IAPs). Understanding and modelling of viral escape mechanisms and the dynamics of IAP action has the potential to facilitate the development of specific and safe drugs. Here, we describe the dynamics of interference by selected viral IAPs, NS1 from Influenza A virus and NS3/4A from Hepatitis C virus. We used Tet-inducible IAP gene expression to uncouple this process from virus-driven dynamics. Stochastic activation of the IFN-β gene required the use of single-cell live imaging to define the efficacy of the inhibitors during the virus-induced signalling processes. We found significant correlation between the onset of IAP expression and halted IFN-β expression in cells where IFN-β induction had already occurred. These data indicate that IAPs not only prevent antiviral signalling prior to IFN-β induction, but can also stop the antiviral response even after it has been activated. We found reduced NF-κB activation to be the underlying mechanism by which activated IFN expression can be blocked. This work demonstrates a new mechanism by which viruses can antagonise the IFN response.     

Using gravel for environmental enrichment in salmonid hatcheries: The effect of gravel size during egg incubation,endogenous and first feeding in rainbow trout

Environmental enrichment aims for a deliberate increase in structural complexity in otherwise plain rearing units, helping to reduce aberrant traits and promote welfare of fish kept in captivity. Before putting enrichment protocols into practice, however, practitioners like hatchery managers need clear guidelines on enrichment measures and on the substrates used. In the present study, we used rainbow trout as a model species for salmonid rearing and investigated the use of a single layer of three different gravel types, i.e., small (4–8 mm), medium (8–16 mm) and large (16–32 mm), for environmental enrichment during egg incubation, endogenous and first feeding of rainbow trout and compared this to a barren control. From the egg stage onwards, we determined mortality, fungal prevalence as well as growth of larvae and fingerlings. We found that gravel size significantly affected mortality and fungal prevalence with the smallest gravel size and the control showing the lowest incidents. Growth of larvae and fingerlings was not affected by gravel, both when compared between gravel types and to the barren control. When using gravel for environmental enrichment in salmonid hatcheries, a small gravel size should be used. Small gravel provides the fish with a more natural environment without compromising practical feasibility of enrichment in hatcheries, still allowing for easy visual inspection and manual control of the reared fish.     

Use of the parmbsc0 force field and trajectory analysis to study the binding of netropsin to the DNA fragment (5'CCAATTGG)(2) in the presence of excess NaCl salt in aqueous solution

The parmbsc0 force field was applied to study in detail the binding of netropsin, at a salt concentration of 0.28M Na(+), to the minor groove of an 8-mer (5'CCAATTGG)(2) DNA duplex forming a netropsin·DNA complex which previously has been characterized by X-ray crystallography, albeit with the use of closely related DNA duplexes. The X-ray structure revealed that the terminal guanidinium and amidinium groups of netropsin interact with the extreme ends of the palindromic AATT sequence of the receptor DNA. The parmbsc0 parameters of B-DNA and AMBER v9 parameters of netropsin generated a stable 6ns molecular dynamics (MD) trajectory for a 1:1 class I binding motif of this complex. Trajectory analysis for the salt and hydration effects on the binding of netropsin to the 8-mer DNA duplex revealed that 18 water molecules and 2 Na(+) are displaced from the DNA upon netropsin binding. A hydration density map of the complex parallels the X-ray data showing that two structured water molecules are localized near the netropsin guanidinium and amidinium groups forming H-bond bridges between the receptor and the ligand.     

Influence of dietary non-essential amino acid profile on growth performance and amino acid metabolism of Nile tilapia, Oreochromis niloticus (L.)

The quality of dietary protein is an important factor influencing the growth performance of fish. To evaluate the quality of protein, the variables commonly studied are the composition of the essential amino acids, the digestibility and the protein use efficiency. The goal of the present experiment was to test the effect of the dietary non-essential amino acid composition on the growth of Nile tilapia (Oreochromis niloticus). The fish were fed three purified diets differing only in their non-essential amino acid composition. The influence of the experimental diets on the growth performance, on the activity of enzymes involved in the amino acid metabolism, aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT), and on whole body delta(15)N values was investigated. Body mass, lipid, protein and energy gain differed significantly between the feeding groups. The activity of ASAT in the whole liver was significantly higher in fish with a positive protein balance compared to fish which lost protein. Whole body delta(15)N values of fish were negatively correlated with their body mass gain. Despite the poor utilisation of synthetic amino acids, the experiment indicates the importance of the dietary non-essential amino acid composition for the growth performance of fish. The study reveals the possibility to trace the utilisation of synthetic amino acids by determining the isotopic composition of dietary amino acids and tissues or whole bodies of animals.     

Microcystins in natural blooms and laboratory cultured Microcystis aeruginosa from Laguna de Bay,Philippines

Laguna de Bay, the largest freshwater lake in the Philippines, experiences periodic blooms of the cyanobacteria Microcystis aeruginosa. Blooms of these cyanobacteria in 1996, 1998 and 1999 were sampled. HPLC and MALDI-TOF mass spectrometry were used to analyze for microcystins. A total of 16 structural variants of the toxin were isolated from the samples with microcystin LR (MC-LR) as the most abundant variant in the samples from 1996 and 1999 making up 77 to 85% of the total, respectively. MC-RR was the dominant variant in the 1998 bloom making up 38%. The samples from 1996 had the highest total toxin concentration (4049 microg g(-1)) followed by those from 1998 (1577 microg g(-1)) and 1999 (649 microg g(-1)). A strain of M. aeruginosa previously isolated from the lake was also cultured in the laboratory under different nitrogen concentrations (1, 3 and 6 mg L(-1)) and elevated phosphorus concentration (0.5 mg L(-1)) to determine the influence of these factors on toxin production. A total of 9 different structural variants of microcystin were isolated from the laboratory cultures with MC-LR consisting more than 75% of the total in all treatments. No significant differences in the total toxin concentration as well as the % distribution of the different variants among treatments were observed. However, the strain of M. aeruginosa cultured in the laboratory had from 3 to 20 times higher total microcystin than those harvested from the lake.