bluuebunny/crossref_metadata_2025 huggingface dataset:
Membrane reactor technology for C
5
/C
6
hydroisomerization
Authors: McLeary E.E , Buijsse E.J.W , Gora L , Jansen J.C , Maschmeyer Th
Published: April 2005

In this paper, we propose an improved hydroisomerization process, making use of membrane reactor technology. Linear alkanes are selectively supplied from a hydrocarbon feed (consisting of branched and linear alkanes) through an inert tubular membrane to a packed bed of catalyst. The results indicate that
n
-, mono- and di-branched components in a gas mixture can be separated with a selectivity factor of greater than 20 with a zeolite membrane under dedicated parameter settings. The RON-value of the product was calculated to be as high as 90 in a single pass reactor, which is 50 points higher than the feed value. The flux through the membrane could be optimized to give a STY/ATY ratio for the reactor of 877 m
−1
, which falls within the limits of technical feasibility.
Multiple branches of the meiotic recombination pathway contribute independently to homolog pairing and stable juxtaposition during meiosis in budding yeast
Authors: Peoples-Holst Tamara L. , Burgess Sean M.
Published: April 2005

A unique aspect of meiosis is the segregation of homologous chromosomes at the meiosis I division. Homologs are physically connected prior to segregation by crossing over between nonsister chromatids. Crossovers arise from the repair of induced double-strand breaks (DSBs). In many organisms, more DSBs are formed than crossovers in a given nucleus. It has been previously suggested that repair of DSBs to noncrossover recombination products aids homolog alignment. Here we explore how two modes of the meiotic recombination pathway (crossover and noncrossover) and meiotic telomere reorganization contribute to the pairing and close juxtaposition of homologous chromosomes in budding yeast. We found that intermediates in the DSB repair pathway leading to both crossover and noncrossover recombination products contribute independently to close, stable homolog juxtaposition (CSHJ), a measurable state of homolog pairing. Analysis of the ndj1Δ mutant indicates that the effect of meiotic telomere reorganization on CSHJ is exerted through recombination intermediates at interstitial chromosomal loci, perhaps through the noncrossover branch of the DSB repair pathway. We suggest that transient, early DSB-initiated interactions, including those that give rise to noncrossovers, are important for homolog recognition and juxtaposition.
Whole genome shotgun sequencing ofBrassica oleraceaand its application to gene discovery and annotation inArabidopsis
Authors: Ayele Mulu , Haas Brian J. , Kumar Nikhil , Wu Hank , Xiao Yongli , Van Aken Susan , Utterback Teresa R. , Wortman Jennifer R. , White Owen R. , Town Christopher D.
Published: April 2005

Through comparative studies of the model organismArabidopsis thalianaand its close relativeBrassica oleracea, we have identified conserved regions that represent potentially functional sequences overlooked by previousArabidopsisgenome annotation methods. A total of 454,274 whole genome shotgun sequences covering 283 Mb (0.44×) of the estimated 650 MbBrassicagenome were searched against theArabidopsisgenome, and conservedArabidopsisgenome sequences (CAGSs) were identified. Of these 229,735 conserved regions, 167,357 fell within or intersected existing gene models, while 60,378 were located in previously unannotated regions. After removal of sequences matching known proteins, CAGSs that were close to one another were chained together as potentially comprising portions of the same functional unit. This resulted in 27,347 chains of which 15,686 were sufficiently distant from existing gene annotations to be considered a novel conserved unit. Of 192 conserved regions examined, 58 were found to be expressed in our cDNA populations. Rapid amplification of cDNA ends (RACE) was used to obtain potentially full-length transcripts from these 58 regions. The resulting sequences led to the creation of 21 gene models at 17 newArabidopsisloci and the addition of splice variants or updates to another 19 gene structures. In addition, CAGSs overlapping already annotated genes inArabidopsiscan provide guidance for manual improvement of existing gene models. Published genome-wide expression data based on whole genome tiling arrays and massively parallel signature sequencing were overlaid on theBrassica–Arabidopsisconserved sequences, and 1399 regions of intersection were identified. Collectively our results and these data sets suggest that several thousand newArabidopsisgenes remain to be identified and annotated.
Construction of a mini-Tn5-luxCDABE mutant library in Pseudomonas aeruginosa PAO1: A tool for identifying differentially regulated genes
Authors: Lewenza Shawn , Falsafi Reza K. , Winsor Geoff , Gooderham W. James , McPhee Joseph B. , Brinkman Fiona S.L. , Hancock Robert E.W.
Published: April 2005

Pseudomonas aeruginosa is a major cause of nosocomial (hospital-derived) infections, is the predominant pathogen in chronic cystic fibrosis lung infections, and remains difficult to treat due to its high intrinsic antibiotic resistance. The completion of the P. aeruginosa PAO1 genome sequence provides the opportunity for genome-wide studies to increase our understanding of the pathogenesis and biology of this important pathogen. In this report, we describe the construction of a mini-Tn5-luxCDABE mutant library and a high-throughput inverse PCR method to amplify DNA flanking the site of insertion for sequencing and insertion site mapping. In addition to producing polar knockout mutations in nonessential genes, the promoterless luxCDABE reporter present in the transposon serves as a real-time reporter of gene expression for the inactivated gene. A total of 2519 transposon insertion sites were mapped, 77% of which were nonredundant insertions. Of the insertions within an ORF, -55% of total and unique insertion sites were transcriptional luxCDABE fusions. A bias toward low insertion-site density in the genome region that surrounds the predicted terminus of replication was observed. To demonstrate the utility of chromosomal lux fusions, we performed extensive regulatory screens to identify genes that were differentially regulated under magnesium or phosphate limitation. This approach led to the discovery of many known and novel genes necessary for these environmental adaptations, including genes involved in resistance to cationic antimicrobial peptides. This dual-purpose mutant library allows for functional and regulation studies and will serve as a resource for the research community to further our understanding of P. aeruginosa biology.
Intrahippocampal muscimol shifts learning strategy in gonadally intact young adult female rats
Authors: McElroy Molly W. , Korol Donna L.
Published: April 2005

Learning strategy preferences depend upon circulating estrogen levels, with enhanced hippocampus-sensitive place learning coinciding with elevated estrogen levels. The effects of estrogen on strategy may be mediated by fluctuations in GABAergic function, given that inhibitory tone in the hippocampus is low when estrogen is high. We investigated the effects on learning strategy of intrahippocampal injections of a GABAAagonist in gonadally intact female rats. On the day of training, rats received 0.3 μL intrahippocampal infusions of muscimol (0.26 nmol or 2.6 nmol) or saline 20 min prior to training on a T-maze in which place (hippocampus-sensitive) or response (striatum-sensitive) strategies offer effective solutions. Muscimol treatment increased the use of the response strategy in a dose-dependent manner without influencing learning speed, indicating that muscimol modulated strategy and not learning ability. Furthermore, the muscimol-related shift to response strategies varied across the estrous cycle. The results indicate that increasing inhibition in the hippocampus biases rats away from hippocampus-sensitive place learning strategies and toward hippocampus-insensitive response learning strategies without a learning deficit. Furthermore, rats at proestrus demonstrated the most dramatic shift in learning strategy following muscimol treatment compared with control conditions, while rats at estrus demonstrated the most complete bias toward response strategies. The enhanced use of hippocampus-sensitive strategies at proestrus likely results from reduced hippocampal inhibition.
Expression of the immediate-early gene–encoded protein Egr-1
(zif268) during in vitro classical conditioning
Authors: Mokin Maxim , Keifer Joyce
Published: April 2005

Expression of the immediate-early genes (IEGs) has been shown to be induced
by activity-dependent synaptic plasticity or behavioral training and is
thought to play an important role in long-term memory. In the present study,
we examined the induction and expression of the IEG-encoded protein Egr-1
during an in vitro neural correlate of eyeblink classical conditioning. The
results showed that Egr-1 protein expression as determined by
immunocytochemistry and Western blot analysis rapidly increased during the
early stages of conditioning and remained elevated during the later stages.
Further, expression of Egr-1 protein required NMDA receptor activation as it
was blocked by bath application of AP-5. These findings suggest that the
IEG-encoded proteins such as Egr-1 are activated during relatively simple
forms of learning in vertebrates. In this case, Egr-1 may have a functional
role in the acquisition phase of conditioning as well as in maintaining
expression of conditioned responses.
Acute stress facilitates trace eyeblink conditioning in C57BL/6 male mice and increases the excitability of their CA1 pyramidal neurons
Authors: Weiss Craig , Sametsky Evgeny , Sasse Astrid , Spiess Joachim , Disterhoft John F.
Published: April 2005

The effects of stress (restraint plus tail shock) on hippocampus-dependent trace eyeblink conditioning and hippocampal excitability were examined in C57BL/6 male mice. The results indicate that the stressor significantly increased the concentration of circulating corticosterone, the amount and rate of learning relative to nonstressed conditioned mice, and the excitability of CA1 hippocampal pyramidal neurons. Behaviorally, there was no effect of the stressor on control mice that received unpaired presentations of the tone and periorbital shock, i.e., neither stressed nor nonstressed control mice showed an increase in conditioned responding that was above baseline levels. Biophysically, the stressor significantly decreased the amplitude of the post-burst afterhyperpolarization (AHP) and decreased spike frequency accommodation relative to cells from nonstressed control mice. The effect was significant for mice that were stressed either 1 h or 24 h earlier. The results suggest that the stressor increases the excitability of hippocampal pyramidal neurons and that the mechanism underlying this increase may contribute to the more rapid acquisition of hippocampally dependent eyeblink conditioning.
A role for prefrontal calcium-sensitive protein phosphatase and kinase activities in working memory
Authors: Runyan Jason D. , Moore Anthony N. , Dash Pramod K.
Published: April 2005

The prefrontal cortex is involved in the integration and interpretation of
information for directing thoughts and planning action. Working memory is
defined as the active maintenance of information in mind and is thought to lie
at the core of many prefrontal functions. Although dopamine and other
neurotransmitters have been implicated, the intracellular events activated by
their receptors that influence working memory are poorly understood. We
demonstrate that working memory involves transient changes in prefrontal
Gq/11-signaling and in calcium-dependent intracellular protein
phosphatase and kinase activity. Interestingly, inhibition of the calcium
activated phosphatase calcineurin impaired, while calcium/calmodulin dependent
kinase II (CaMKII) and calcium-dependent protein kinase C (PKC) enhanced,
working memory. Our findings suggest that the active maintenance of
information required for working memory involves transient changes in the
balance of these enzymes' activities.
Identification of mouse brain proteins associated with isoform 3 of metallothionein
Authors: Lahti David W. , Hoekman John D. , Tokheim Abigail M. , Martin Bruce L. , Armitage Ian M.
Published: April 2005

Using immunological approaches and mass spectrometry, five proteins associated with metallothionein‐3 in mouse brains have been identified. Metallothionein‐3 and associated proteins were isolated using immunoaffinity chromatography over immobilized anti‐mouse brain MT3 antibody. Proteins in the recovered pool were separated by SDS‐polyacrylamide gel electrophoresis, and distinct bands were excised and the proteins digested using trypsin. Peptides were extracted and analyzed using electrospray ionization mass spectrometry. Initial identification was done comparing the identified peptide mass:charge ratios to the MASCOT database. Confirmation of proteins was accomplished by sequencing of selected peptides using tandem mass spectrometry and comparison to the MASCOT database. The proteins were heat‐shock protein 84 (mouse variant of heat‐shock protein 90), heat‐shock protein 70, dihydropyrimidinase‐like protein 2, creatine kinase, and β actin. Independently using antibodies against metallothionein‐3, creatine kinase, and heat‐shock protein 84 showed that all three proteins were coimmunoprecipitated from whole mouse brain homogenates with each of the three antibodies. Mixing purified samples of metallothionein and human brain creatine kinase also generated a complex that could be immunoprecipitated either by anti‐metallothionein‐3 or anticreatine kinase antibody. These data are consistent with metallothionein‐3 being present in the mouse brain as part of a multiprotein complex providing new functional information for understanding the role of metallothionein‐3 in neuronal physiology.
Enterococcus faecalis phosphomevalonate kinase
Authors: Doun Stephanie S. , Burgner John W. , Briggs Scott D. , Rodwell Victor W.
Published: April 2005

The six enzymes of the mevalonate pathway of isopentenyl diphosphate biosynthesis represent potential for addressing a pressing human health concern, the development of antibiotics against resistant strains of the Gram‐positive streptococci. We previously characterized the first four of the mevalonate pathway enzymes of Enterococcus faecalis, and here characterize the fifth, phosphomevalonate kinase (E.C. 2.7.4.2). E. faecalis genomic DNA and the polymerase chain reaction were used to clone DNA thought to encode phosphomevalonate kinase into pET28b(+). Double‐stranded DNA sequencing verified the sequence of the recombinant gene. The encoded N‐terminal hexahistidine‐tagged protein was expressed in Escherichia coli with induction by isopropylthiogalactoside and purified by Ni++ affinity chromatography, yield 20 mg protein per liter. Analysis of the purified protein by MALDI‐TOF mass spectrometry established it as E. faecalis phosphomevalonate kinase. Analytical ultracentrifugation revealed that the kinase exists in solution primarily as a dimer. Assay for phosphomevalonate kinase activity used pyruvate kinase and lactate dehydrogenase to couple the formation of ADP to the oxidation of NADH. Optimal activity occurred at pH 8.0 and at 37°C. The activation energy was ∼5.6 kcal/mol. Activity with Mn++, the preferred cation, was optimal at about 4 mM. Relative rates using different phosphoryl donors were 100 (ATP), 3.6 (GTP), 1.6 (TTP), and 0.4 (CTP). Km values were 0.17 mM for ATP and 0.19 mM for (R,S)‐5‐phosphomevalonate. The specific activity of the purified enzyme was 3.9 μmol substrate converted per minute per milligram protein. Applications to an immobilized enzyme bioreactor and to drug screening and design are discussed.
Direct estimates of the selectivity of a multimesh and a series of single gillnets for brown trout
Authors: Jensen J. W. , Hesthagen T.
Published: April 2005

Hatchery brown trout Salmo trutta (1406) of length 5–20 cm were released into a 7.5 ha shallow lake. They were recaptured with 28 multimesh gillnets of a type proposed for use in the Nordic countries and 42 single gillnets of mesh size 8–22 mm (knot to knot). Corrected for the effect of different twine thicknesses, the single nets showed the highest selectivity for 16.5 mm and smaller meshes and the multimesh nets for the larger meshes. The height of the selectivity curves increased exponentially with mesh size, and most distinctly for the multimesh nets. Over a limited range of mesh sizes the selectivity of the two types of net did not differ much. Extended over mesh sizes 10.0–55.0 mm, the catching abilities of the two types of net became considerably different.
Exposure of goldsinny, rock cook and corkwing wrasse to low temperature and low salinity: survival, blood physiology and seasonal variation
Authors: Sayer M. D. J. , Reader J. P.
Published: April 2005

Wrasse used as cleaner fish with farmed Atlantic salmon Salmo salar can be subjected to large and rapid temperature and salinity fluctuations in late autumn and early winter, when summer‐warmed surface water is affected by early snowmelt episodes. Because of their containment in sea cages, wrasse which are essentially acclimated to summer temperatures may be rapidly exposed to winter conditions. Short‐term tolerance of low temperature and low salinity by three species of wrasse, goldsinny Ctenolabrus rupestris rock cook Centrolabrus exoletus corkwing Crenilabrus melops caught during the summer, and winter‐caught corkwing, was investigated. A 3–day period at 30 or 32‰ salinity and temperature 8, 6 or 4° C (for summer‐caught fish; 4° C only for winter‐caught) was followed by a decline in salinity to 24, 16 or 8‰ over c. 36 h, followed by a further 24 h at these salinities held constant, at each of the three temperatures. Controls in 30 or 32‰ were maintained at 8, 6 or 4° C. Mortality of summer‐caught corkwing and rock cook was high at 4° C, whereas the influence of salinity on mortality was small. Mortality of goldsinny was low or zero in all treatments. Surviving corkwing and rock cook after 3 days at 4° C and 32‰ salinity had elevated plasma osmolality: in summer‐caught corkwing, plasma [Cl°] and [Na+] were high, whereas in rock cook only [Na+] was high. Haematocrit was low in summer‐caught corkwing, high in rock cook. In survivors of all three species at the end of the experiment, values of all these parameters were comparable with those of fish at the beginning of the experiment, except that survivors at low salinity (8, 16‰) had low plasma osmolality, at all temperatures, and in surviving rock cook in these treatments haematocrit was high and plasma [Cl−] was low. Winter‐caught corkwing had higher osmolality, [Na+] and [Cl−] than summer‐caught corkwing; there was no difference in haematocrit. Survival of wintercaught corkwing exposed to four salinities at 4° C was much higher than that of summercaught corkwing under the same conditions. Little change in blood physiology was recorded for winter‐caught corkwing, with only fish subjected to 8‰ and 4° C showing signs of osmoregulatory stress. The interspecific and seasonal differences in survival and blood physiology at low temperature and low salinity are discussed in relation to wrasse survival over winter, both in the field and in salmon farms.
Hypometabolism in torpid goldsinny wrasse subjected to rapid reductions in seawater temperature
Authors: Sayer M. D. J. , Davenport J.
Published: April 2005

Goldsinny Ctenolabrus rupestris were subjected to rapid, environmentally realistic, reductions in temperature at 2° C increments from 10 to 4° C over a 3‐day period in full‐strength sea water. In separate experiments, oxygen uptake measurements and ultrasound recordings of heart rate and opercular motion were carried out at regular intervals over the same temperature regime. Mean oxygen uptake rates fell from 0.042 to 0.028 ml O2 g−1 h−1 between 10 and 6° C respectively (Q10=2.71). Between 6 and 4° C mean rates decreased from 0.028 to 0.008 ml O2 g−1 h−1 (Q10=542). Mean opercular motion and heart beat rates decreased from 49.5 and 60.3 beats min−1 respectively at 10° C to 18.7 and 18.0 beats min−1 respectively at 4° C. Most goldsinny subjected to 4° C were observed in a torpid state and would not react to external stimulation. Opercular motion was erratic at 4° C and would at times cease altogether for periods up to 1.3 min duration. Heart movement was diffcult to detect at 4° C and may also have ceased for prolonged periods. Q10 values for opercular motion and heart beat rates recorded between 6 and 4° C were 6.39 and 24.52 respectively compared with values of 2.42 and 2.93 respectively recorded between 10 and 8° C. Such large depressions in metabolism appear not to have been reported previously for a marine fish species. No goldsinny mortalities were recorded at any temperature. The possibility that hypometabolic torpor is an adaptive strategy for goldsinny survival at low environmental temperatures is discussed.
Date of smolt migration depends on body‐size but not age in wild sea‐run brown trout
Authors: Bohlin T. , Dellefors C. , Faremo U.
Published: April 2005

Wild, one‐ and two‐summers‐old sea‐trout parr in a small stream, were tagged with PIT‐tags in late autumn and recaptured in a smolt trap during the following spring. One‐summer‐old smolts migrated later than older ones and were smaller at migration. ANCOVA indicated that migration date was negatively related to body length at tagging, but we found no significant effect of age or condition factor at tagging on this relation. The difference in timing between the age‐classes was thus an effect of body size rather than age.
Plasma ammonia and urea levels in Atlantic salmon farmed in sea water
Authors: Knoph M. B. , Måsøval K.
Published: April 2005

Plasma ammonia and urea levels were measured in feeding Atlantic salmon Salmo salar L. reared in two different commercial Norwegian sea farms. A very large individual variation of the plasma ammonia and urea levels in addition to the large influence of several factors suggest that it may be difficult to use these parameters in diagnostic work on fish.
The limitations of heart rate as a predictor of metabolic rate in fish
Authors: Thorarensen H. , Gallaugher P. E. , Farrell A. P.
Published: April 2005

Although telemetered heart rate (fH) has been used as a physiological correlate to predict the metabolic rate (as oxygen consumption, V̇O2) of fish in the field, it is our contention that the method has not been validated adequately for fish. If fH in fish is to be used to estimate V̇O2, a single linear (or log‐linear) relationship must be established for each species between the two variables which allows V̇O2 to be predicted accurately under all environmentally relevant conditions. Our analyses of existing data indicate that while a good linear (or log‐linear) relationship can be established between fH and V̇O2, the conditions under which the relationship applies may be quite restricted. Physiological states and environmental factors affect the relationship between fH and V̇O2 significantly such that several curves can exist for a single species. In addition, there are situations in which fH and V̇O2 do not covary in a significant manner. In some situations fH can vary over much of its physiological range while V̇O2 remains constant; in others V̇O2 may vary while fH is invariate. The theoretical basis for this variability is examined to explain why the use of telemetered fH in predicting V̇O2 of fish may be limited to certain specified applications.
Aggressive behaviour of underyearling rainbow trout in simulated winter concealment habitat
Authors: Gregory J. S. , Griffith J. S.
Published: April 2005

The behaviour of wild underyearling rainbow trout Oncorhynchus mykiss in concealment habitat in a laboratory stream aquarium at 2 and 6°C was recorded daily with an infrared video camera for 90 min over dawn. Aggressive behaviours (threat nips, nips and chases) were frequent during this time as fish entered concealment habitat. Aggressiveness varied widely among fish groups, with a range of 1 to 45 aggressive acts being initiated during a 90‐min filming period. Larger fish initiated most of the encounters and removed a higher proportion of fish from concealment than did smaller aggressors. Thirteen per cent of the aggressive acts resulted in the recipient being completely removed from concealment habitat. The highest combined frequency of aggressive acts was 0.64 per visible fish per 10 min period and occurred at relatively low light levels (300 lx). The data suggest that when fish density is high, such as when habitat is limited, aggressive behaviour in winter may cause some underyearling salmonids to be excluded from concealment.
Food‐ and habitat‐segregation in sympatric grayling and brown trout
Authors: Haugen T. O. , Rygg T. A.
Published: April 2005

Grayling in the large reservoir Aursjøen, Norway, did not use the pelagic habitat and only trout larger than 187 mm and older than 4+ were caught there. Both species preferred the upper 8 m in the benthic habitat, but grayling were caught deeper than trout in August and September. Grayling were more closely associated with soft substratum than trout. Association with soft substratum decreased with increasing size in grayling, whereas this relationship was reversed in trout. A low number of empty stomachs indicated a low degree of food competition, but despite this the two species segregated in different key prey items—probably due to differences in mouth shapes. The key prey item for grayling was the benthic Eurycercus lamellatus, with zooplankton dominating the diet of the smallest individuals. Large trout (>300 mm) preferred the benthic Lepidurus arcticus, whereas medium trout (160–300 mm) ate predominantly the limnic‐pelagic Bythotrephes longimanus, irrespective of habitat. The distribution of key prey items seemed to be the major factor controlling the habitat use, except in small trout which showed a generalist feeding pattern throughout the period. A generalist feeding pattern, a close association to coarse substratum and absence from the pelagic habitat indicated that small trout were negatively influenced by large individuals. Small grayling seemed less affected by aggressive encounters as they were less associated with coarse substratum and ate predominantly high‐risk food such as zooplankton. These individuals probably did shoal in order to reduce predation risk.
How puffers (Teleostei: Tetraodontidae) swim
Authors: Gordon M. S. , Plaut I. , Kim D.
Published: April 2005

Two species of marine Indo‐Pacific puffers, Arothron meleagris and A. nigropunctatus, were filmed with a high‐speed motion picture camera while swimming in a Brett‐type water tunnel at speeds of 1‐3.5 body lengths (BL) s−1. The puffers generated thrust by use of their pectoral fins in addition to their dorsal and anal fins; the long axis of the body tilted, mouth upwards, by 3–10) while the fishes swam; antero‐ventral body profiles of the fishes changed as swimming speeds increased; pectoral fins undulated and moved 180) out of phase from each other, while dorsal and anal fins oscillated in phase with each other; frequencies of fin movements (F) increased linearly in relation to swimming speeds (Uc(rel)) and were described by the equation F=1.48 Uc(rel)+1.66; stride lengths also increased at higher Uc(rel); and, at swimming speeds above 3.0 BL s−1 puffers began to move their tails in sub carangiform‐like modes of burst swimming. These results modify significantly the accepted view of the tetraodonti form mode of median and paired fin swimming.
Agonistic behaviour and sound production in Gaidropsarus mediterraneus, (Gadidae)
Authors: Almada V. C. , Amorim M. C. P. , Pereira E. , Almada F. , Matos R. , Godinho R.
Published: April 2005

Agonistic behaviour and sound production were described for captive Gaidropsarus mediterraneus, a shore‐dwelling gadoid. Thump‐like sounds were produced during agonistic interactions, which involved disputes over access to shelter sites.
The competitive advantage of large body size declines with increasing group size in rainbow trout
Authors: Pettersson J. , Johnsson J. I. , Bohlin T.
Published: April 2005

This experimental study supports the hypothesis that the competitive advantage of large body size declines with increasing group size in rainbow trout Oncorhynchus mykiss, (Walbaum).
Population dynamics of Gyrodactylus sp. (Monogenea) infecting the sand goby in the Oslo Fjord, Norway
Authors: Appleby C.
Published: April 2005

Prevalence and abundance of Gyrodactylus sp. on the 1993 year‐class of sand gobies Pomatoschistus minutus in the Oslo Fjord, Norway, decreased slightly during the cold months, increased as temperature increased in spring, reaching a peak in June, then decreased significantly, corresponding with a decline in the number of hosts from August. Abundance and, especially, prevalence increased again in September, and decreased in late autumn. Death of the most heavily infected hosts, and/or host resistance might be responsible for the decline in parasite numbers on post‐spawners in summer. The young of the year (1994 year‐class) were probably infected shortly after they commenced benthic life in July, and prevalence and abundance increased significantly throughout late summer and autumn. Parasite abundance on males was significantly higher than on females at the height of the breeding season in June, but significantly lower at the end of the breeding season in July. Two‐thirds of the parasites infected the gills, oral cavity and pharynx. The proportion of parasites on the body, head and fins increased on both sexes, but significantly more so on males, during the breeding season of the host, when parasite intensity was highest. Possible routes of transmission of the parasite are discussed.
Body condition and reproductive status in sticklebacks exposed to a single wave of Schistocephalus solidus infection
Authors: Tierney J. F. , Huntingford F. A. , Crompton D. W. T.
Published: April 2005

This paper describes the results of a study of the effects of Schistocephalus solidus on one of its intermediate hosts, the stickleback Gasterosteus aculeatus, in an annual population in which infection is known to occur in one major wave in autumn. Weight, as a function of length, was lower in infected sticklebacks compared with uninfected fish during autumn and spring; in winter and summer, both categories of fish were in equally poor condition. In early autumn, the hepatosomatic indices of newly infected fish were higher than those of uninfected fish, perhaps due to a pathological response. Thereafter, relative liver size of uninfected and infected sticklebacks was comparable until spring, when it increased sharply in uninfected sticklebacks but remained stable at a low level in infected sticklebacks. Few infected fish reached maturity. The only males to attain maturity whilst sustaining an infection of S. solidus were in particularly good condition. Nuptial coloration, kidney hypertrophy and testes size were unimpaired in these mature infected males, but whether they were capable of successful reproduction remains debatable.
Gastrointestinal responses of rainbow trout to dry pellet and low‐fat herring diets
Authors: Ruohonen K. , Grove D. J.
Published: April 2005

Long‐term voluntary‐feeding experiments were carried out on farmed, 2‐year‐old rainbow trout offered a commercial dry feed, or chopped low‐fat Baltic herring. Despite large differences in dietary water, protein and lipid content, the trout adjusted their intake to consume similar amounts of dry matter. After an 18‐week trial, the stomach volumes of the herring‐fed trout were significantly larger (30–35%) than those fed on the dry diet. Greatest differences were observed when fish were fed one meal per day; increasing the number of daily feeding opportunities reduced these expected stomach volumes on each diet by 15–20%. The relative increase in stomach volume was shown to be due to growth of the cardiac stomach region (corpus) rather than the pyloric region, and not to muscle relaxation; the change was completed within 10 weeks. Data were collected in a separate study to investigate stomach size in fish (age 0+, 1+, 2+) of similar genetic backgrounds which had been grown using dry pelleted diets. Despite considerable variation between populations, stomach volume to body weight relationship was allometric (S = a Wb) with the exponent in the range of 0.3–0.4.
Characterization of carp thrombocytes with specific monoclonal antibodies
Authors: Rombout J. H. W. M. , Koumans‐van Diepen J. C. E. , Emmer P. M. , Taverne‐Thiele J. J. , Taverne N.
Published: April 2005

Monoclonal antibodies (WCL6) specific for carp Cyprinus carpio thrombocytes were produced by immunizing mice with membrane lysates of IgM‐negative peripheral blood leucocytes (PBL) and selected on the negative reaction with B cells. WCL6 was reactive with a membrane molecule of approximately 90 kDa and to a lesser extent with molecules of approximately 95 and 110 kDa. In general, between 30 and 40% of PBL were WCL6+ and appeared to be round to spindle‐shaped cells. Immunohistochemical analysis of cryo‐sections showed much higher numbers of WCL6+ cells in the spleen than in the pronephros, intestine and thymus. Flow cytometric analysis of cell suspensions isolated from these organs only revealed WCL6+ cells (4–10%) in the spleen. Electron microscopy of immunogold‐stained WCL6+ PBL showed round but also some spindle‐shaped cells with canalicular and granular structures, and a more irregular and electron‐dense nucleus than found in lymphocytes. WCL6+ cells with electrondense pyknotic nuclei (without a clear nuclear envelope) were found also and their frequency increased with the length of the isolation and staining procedure used. In the spleen, several differentiation steps of WCL6+ cells were found and hence the spleen seems to be the thrombopoietic organ in carp. Thrombocytes from blood could be activated with collagen; the collagen‐activated cells showed a higher side (90°) scatter by flow cytometric analysis and finally considerable cell death.
Dietary ascorbic acid requirements during the hatchery production of turbot larvae
Authors: Merchie G. , Lavens P. , Dhert Ph. , Góamez M. García Ulloa , Nelis H. , De Leenheer A. , Sorgeloos P.
Published: April 2005

The effect of high ascorbic acid (AA) levels transferred through enriched live food was evaluated for turbot Scophthalmus maximus larvae in two consecutive feeding experiments. The same feeding strategy was applied to all treatments, except for the AA content of the live food which was manipulated through bioencapsulation with ascorbyl palmitate. This resulted finally in a low, medium and high‐AA treatment. The AA incorporation levels in the turbot larvae (up to 1400 μg AA g DW−1) were correlated with the AA content of the live food administered. However, feeding the high AA concentration resulted in the same values as for the medium treatment, indicating a saturation of the body AA reserves. Under standard culture conditions, no differences in growth nor overall survival could be detected among the different groups, illustrating that the dietary AA requirements of larval turbot are met by non‐enriched live food containing already 500 μg AA g DW−1. The larvae of the high‐AA treatment, however, showed a better pigmentation rate (47 and 32% for experiments 1 and 2, respectively) compared to the other groups (35 and 25%, respectively). Evaluation of the physiological condition applying a salinity stress test revealed an improvement by feeding extra AA, significantly in the medium‐AA treatment. Though not significantly different, cumulative mortalities after challenge with Vibrio anguillarum amounted to 50% for the control v. 40% for the fish fed medium and high‐AA diets, respectively. Moreover, the onset of mortalities in this study was slower (not significantly) for the fish fed the extra AA.
Glycohistochemistry of the Tilapia spp. stomach
Authors: Scocco P. , Ceccarelli P. , Menghi G.
Published: April 2005

A histochemical study using conventional and lectin methods was performed on the stomach of fasting and feeding adults of Tilapia spp. A battery of HRP‐conjugated lectins combined with exoglycosidase digestion was used. The differences found in the epithelium, gastric pits and gastric glands between fasting and feeding subjects were related to the functional stages of the organ. Carbohydrate composition was also compared with that of mammals and birds.
Territorial and non‐territorial spawning behaviour in the bream
Authors: Poncin P. , Philippart J. C. , Ruwet J. C.
Published: April 2005

The spawning behaviour of bream Abramis brama was studied in 1993, in a harbour on the River Meuse, Belgium. Fish spawned from 22 to 27 April and from 11 to 14 May, when the water temperature rose to 14.5) C. The reproductive behaviour of the bream was studied within a 15 m long part of the harbour using a video camera. Territorial males with tubercles (33–43 cm total length; >5 years old) defended bank areas of diameter 80–150 cm which included spawning substratum, i.e. roots of alder and willow trees and aquatic plants. Water depth ranged from 25 to 50 cm. Non‐territorial males without tubercles (24–33 cm; 3–4 years old), remained 2–4 m away from the bank. Aggressive behaviour between males was frequent and, occasionally, males with tubercles were unable to defend a territory. Mature females (25–43 cm; >3 years old), coming from the deeper water of the surrounding area, were followed by non‐territorial males before spawning in territories near the bank.
Effects of temperature on growth and metabolism in juvenile turbot
Authors: Burel C. , Person‐Le Ruyet J. , Gaumet F. , Le Roux A. , Sévère A. , Boeuf G.
Published: April 2005

The effects of constant temperatures on growth, food efficiency, and physiological status were studied in four different batches of juvenile turbot. The growth responses were studied in three experiments lasting 70–85 days under 8–20° C thermal conditions. There was a positive correlation between growth and temperature from 8 to 17° C and a plateau was observed from 17 to 20° C. In fish fed to satiety, specific growth rate was positively correlated to the food intake, which was double at 20° C, compared with 8° C. Minor changes were observed in food efficiency. Body fat deposition decreased as temperature increased (25% lower at 20° C, compared with 8° C). Apparent food conversion, PER (protein efficiency ratio) and PUC (protein utilization coefficient) ranges were 0.8–0.9, 2.1–2.3 and 33–38% respectively. In 70–300 g fish, routine MO2 increased (2.5–6.5 μmol O2 h−1 g bw−1) with temperature up to 20° C, while larger turbot (500–600 g) appeared relatively thermo‐independent, with a lower oxygen consumption (1.5 ìmol h−1 g−1). The average daily total ammonia nitrogen (TAN) and urea‐N excretion per fish biomass was positively related to temperature. TAN was 30% lower at 8° C, compared with 20° C. Ingested nitrogen was mainly excreted under the final form of TAN, urea‐N representing 26% of the total amount. A post‐prandial peak in TAN and a delayed peak in urea‐N nitrogen were observed. The hydromineral status [osmolarity, sodium, chloride and potassium blood plasma, gill (Na+‐K+)‐ATPase activity] of turbot was not affected by progressive changes in temperature during the acclimation period. Juvenile turbots show remarkable homeostatic capacities and so they have a relatively thermo‐independent physiology within the range of temperature studied.
Morphological changes in the gills of Lophiosilurus alexandri exposed to un‐ionized ammonia
Authors: Cardoso E. L. , Chiarini‐Garcia H. , Ferreira R. M. A. , Poli C. R.
Published: April 2005

The average lethal concentration of un‐ionized ammonia (48‐h LC50NH3) has been determined by the static assay for larvae (0.48 mg l−1) and alevins (0.92 mg l−1) of ‘pacamã’Lophiosilurus alexandri. Studies by light and scanning electron microscopes at the greatest concentration of NH3 (0.99 mg l−1 for larvae and 1.5 mg l−1 for alevins) have shown that the changes in the cells and branchial tissue were more intense in the alevins.
Changes in chloride cell distribution during early larval stages of Clupea harengus
Authors: Wales W. , Tytler P.
Published: April 2005

A non‐uniform distribution of cutaneous chloride cells was found in the early, pre‐feeding larval stages of herring Clupea harengus. Chloride cells on the head, yolk‐sac and trunk regions were unevenly distributed, whereas more densely packed chloride cells were observed in the pericardial and prebranchial regions. The pattern of chloride cell distribution changed during development and two distinct changes are described. The density of choride cells on the ventral trunk increased substantially during the period of yolk absorption, presumably due to contraction of the yolk sac and selective retention of yolk‐sac chloride cells. Also during this period the cells on the lateral body wall increased in number and became distributed in segmental bands overlying the myosepta. Most chloride cells were found in association with the haemocoel or primordial blood vessels. Superficial segmental blood vessels were not found in the early larva, but the segmental bands of chloride cells overlay nerve tracts in the myosepta which were tentatively identified as the focal innervation of myotomes. It is concluded that both the circulatory system and the peripheral nervous system may play a role in determining chloride cell distribution in early larvae.
Evolutionary and taxonomic relationships among Far‐Eastern salmonid fishes inferred from mitochondrial DNA divergence
Authors: Shed'ko S. V. , Ginatulina L. K. , Parpura I. Z. , Ermolenko A. V.
Published: April 2005

Mitochondrial DNA (mtDNA) restriction analysis was used to examine the evolutionary and taxonomic relationships among 11 taxa of the subfamily Salmoninae. The genera Brachymystax and Hucho were closely related, diverging by sequence divergence estimates of 3.1%. Because the mtDNA sequence divergence between blunt‐ and sharp‐snouted forms of Brachymystax (2.24%) was similar to divergence level of Brachymystax and Hucho, then taking into account the distinct morphological, ecological and allozyme differences between them, it is possible to recognize these forms as two separate species. The subgenus Parahucho formed a very distinct group differing by 6.35–7.08% (sequence divergence estimate) from both Brachymystax and Hucho and must be considered as a valid genus. The UPGMA and neighbour‐joined phenograms showed that the five genera studied are divided into two main groupings: (1) Hucho, Brachymystax and Salvelinus; and (2) Oncorhynchus and Parahucho species. The mtDNA sequence divergence estimates between these groupings were about 8.1%. However, the subsequent bootstrap analysis of mtDNA RFLP data did not support the monophyly of the latter grouping. The concordance of morphological and mtDNA phylogenetic patterns is discussed.
Effect of ration and body size on the energy budget of juvenile white sturgeon
Authors: Cui Y. , Hung S. S. O. , Zhu X.
Published: April 2005

Growth and energy budget were measured for three sizes (2.4, 11.1 and 22.5 g) of juvenile white sturgeon Acipenser transmontanus held at 18.5° C and fed tubificid worms at different levels ranging from starvation to ad libitum. For each size‐class, specific growth rate increased linearly with increasing ration, and conversion efficiency was highest at the maximum ration. Growth rate decreased with increasing fish size at the maximum ration, but increased with size at each restricted ration. Conversion efficiency increased with increasing ration for each size‐class and was usually highest at the maximum ration. Faecal production accounted for 3.2–5.2% of food energy. The proportion of food energy lost in nitrogenous excretion decreased with increasing ration. With increases in ration, the allocation of metabolizable energy to metabolism decreased, while that to growth increased. Fish size had no significant effect on the allocation of metabolizable energy to metabolism or growth. At the maximum ration, on average 64.9% of metabolizable energy was spent on metabolism, and 35.1% on growth.
Formation of the enveloping layer of the chum salmon egg in isotonic salt solutions
Authors: Yamamoto T. S. , Kobayashi W.
Published: April 2005

After stimulation in a hypotonic solution (9.4 mOsm kg−1), inseminated eggs of the chum salmon Oncorhynchus keta initiate cleavages in isotonic salmon Ringer's solution (267.3 mOsm kg−1) containing 3.2 mM Ca2+ ions. Blastomeres of these eggs, however, separate from each other and the enveloping layer is not observed at the blastula stage. An increase in external divalent cations rescues the separation; the concentration of CaCl2 in the external medium should be 25 mM or more to induce close contact of blastomeres and the formation of an enveloping layer in isotonic salt solutions. The effectiveness of Ca2+ ions can be substituted by Mg2+, Sr2+ and Zn2+ ions; the same results are obtained in isotonic MgCl2 and SrCl2 solutions (100 mM) or in isotonic salmon Ringer's solution containing Zn ions (6.2 mM). The close contact of blastomeres and the formation of an enveloping layer are also observed in a low Ca2+ concentration (< 0.1 mM) in a hypotonic salt solution (9.4 mOsm kg−1). The Ca2+ level in the external medium to induce the enveloping layer formation seems to be correlated with the salinity of the incubation medium. It is suggested that adhesion molecules on the surface of blastomeres in the chum salmon eggs are different in properties from those found in sea urchin and other fish species.
Implications of individual growth status on the future sex of the European eel
Authors: Holmgren K. , Mosegaard H.
Published: April 2005

Sex‐related differences in growth status was demonstrated in eels Anguilla anguilla reared indoors at 17, 20 or 26° C, from the elver stage. Growth status was defined as length increase, weight increase and length–weight relationship. Eels attaining at least 10 g body weight (180–220 mm body length) were tagged with Passive Integrated Transponders (PIT). Length and weight were measured at 6‐week intervals, until individuals stopped growing or had attained 150 g weight (380–450 mm). Sex‐specific data from potentially undifferentiated eels were provided by retrospective classification of sex. Comparisions between sexes were made within groups graded by length or weight data from the beginning of each 6‐week period. There was no consistent difference in absolute length increase between small males and females, but below 40–60 g initial body weight, males displayed on average a higher weight increase than females. Males also had lower length at weight than females, even in the smallest weight groups. Early growth status may influence the future sex of undifferentiated eels, but other approaches are needed for distinction between cause and effect.
The interaction of temperature and fish size on growth of juvenile turbot
Authors: Imsland A. K. , Sunde L. M. , Folkvord A. , Stefansson S. O.
Published: April 2005

Growth rate of tagged juvenile turbot was significantly influenced by the interaction of temperature and fish size. The results suggest the optimum temperature for growth of juvenile turbot in the size range 25–75 g is between 16 and 19°C. Optimal temperature for growth decreased rapidly with increasing size, and is between 13 and 16°C for 100 g turbot. Although individual growth rates varied highly at all times within the temperature treatments, significant size rank correlations were maintained during the experimental period. The study confirms that turbot exhibit ontogenetic variation in temperature optimum, which might partly explain different spatial distribution of juvenile and adult turbot in ocean waters.