Studies on infectious pancreatic necrosis virus interactions with RTG-2 and FHM cells: selection of a variant virus-type in FHM cells.
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Evidence is presented that adaptation of IPN virus (strain VR 299) to FHM cells entails the selection of a variant virus type that differs significantly from the parental, and most representative, RTG-2 virus type in being able to adsorb efficiently to, and form plaques in, FHM cells. The plaque titre of FHM-non-adapted virus stocks (RTG-2 viruses) was reduced by at least 99-99% in FHM cells, while FHM-adapted virus stocks (FHM viruses) produced plaques at equally high titres in both RTG-2 and FHM cells. FHM viruses and RTG-2 viruses differed also in their behavior in RTG-2 cells in respect to plaque size distribution and growth characteristics, but both virus-types were shown to be morphologically identical, and no significant difference in reactivity against specific antiserum could be detected. Analysis of virus in individual RTG-2 plaque isolates or plaque progeny shows that a mutation of relatively high frequency (10(-4) to 10(-5))robably causes the ability to infect the FHM cells efficiently. Only these mutant virus-types were found in FHM plaque isolates. (+info)
Kinematic analysis of a novel feeding mechanism in the brook trout Salvelinus fontinalis (Teleostei: Salmonidae): behavioral modulation of a functional novelty.
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The tongue-bite apparatus (TBA) of salmonids represents an impressive novel feeding mechanism. The TBA consists of a set of well-developed teeth on the dorsal surface of the anterior hyoid (basihyal) and an opposing set of teeth on the roof of the mouth (vomer). A kinematic analysis of behaviors associated with the TBA in the brook trout Salvelinus fontinalis was performed using high-speed video (250 frames s(-1)). Two distinct behaviors were identified, raking and open-mouth chewing. Univariate analysis demonstrated that these behaviors were significantly different from one another. The power stroke of raking is characterized by significantly greater neurocranial elevation (raking, 36 degrees; open-mouth chewing, 16 degrees ) and retraction of the pectoral girdle (raking, 0.85 cm or 21 % of head length; open-mouth chewing, 0.41 cm or 10 % of head length). Open-mouth chewing is characterized predominantly by dorso-ventral excursions of the anterior hyoid (open-mouth chewing, 0.26 cm; raking, 0.14 cm). Raking is significantly shorter in duration (mean 49 ms) than open-mouth chewing (mean 77 ms). When presented with three different types of prey (crickets, fish or worms), Salvelinus fontinalis showed no variation in raking behavior, indicating that raking is highly stereotyped. In contrast, when feeding on worms, Salvelinus fontinalis modulated open-mouth chewing behavior with shorter durations to maximum displacement (at least 20 ms shorter than for either fish or cricket), although the magnitude of displacements did not vary. The reasons for the shorter duration of displacement variables while feeding on worms remains unclear. During post-capture processing behaviors in Salvelinus fontinalis, the magnitude of displacement variables is highly variable between individuals, but temporal patterns are not. This study characterizes two novel post-capture feeding behaviors and modulation of those behaviors in salmonids. (+info)
Isolation and characterisation of rhabdovirus from wild common bream Abramis brama, roach Rutilus rutilus, farmed brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss in Northern Ireland.
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Rhabdovirus was isolated from wild common bream Abramis brama during a disease outbreak with high mortality in Northern Ireland during May 1998. Rhabdovirus was also isolated at the same time from healthy farmed rainbow Oncorhynchus mykiss and brown trout Salmo trutta on the same stretch of river and 11 mo later from healthy wild bream and roach Rutilus rutilus in the same river system. Experimental intra-peritoneal infection of bream and mirror carp Cyprinus carpio var specularis with 2 of these isolates produced low mortality rates of < or = 12%. Serological testing of these isolates by virus neutralisation indicated that they were antigenically closely related to pike fry rhabdovirus (PFRV) but not to spring viraemia of carp virus (SVCV), while testing by enzyme-linked immunosorbent assay indicated them to be antigenically different from both. Comparison of nucleotide sequence data of a 550 base pair segment of the viral glycoprotein generated by reverse transcription-polymerase chain reaction indicated a high (> or = 96.6%) degree of similarity between these isolates and a previous Northern Ireland isolate made in 1984, a 1997 isolate from bream in the Republic of Ireland and an earlier Dutch isolate from roach. In contrast, similarity between these isolates and PFRV was < 82.4%, indicating that these viruses belong to 2 distinct genogroups, while similarity to SVCV was even lower (< 67.4%). (+info)
Sequences of large T1 ribonuclease-resistant oligoribonucleotides from protamine mRNA: the overall architecture of protamine mRNA.
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Limited T1 ribonuclease digestion of the family of protamine mRNA's purified from rainbow trout testis yields several large oligoribonucleotide fragments ranging in size from 12--54 nucleotides in length. Several of these fragments purified by two dimensional gel electrophoresis contain several G residues and must represent nuclease-resistant, base-paired regions of the mRNA. Sequence analysis of these oligonucleotides by the method of Simoncsits, A., Brownlee, G.G., Brown, R.S., Rubin, J.R. and Guilley, H. (1977) Nature 269: 833-836, shows that these oligoribonucleotides arise from the 5'- and 3'-non-coding regions of the mRNA. Comparisons of the sequences of the large RNA fragment with DNA sequences obtained after cloning double-stranded protamine cDNA in the plasmids pBr322 and pmB9 show precise correspondence of a 54 nucleotide RNA fragment with positions 49--100 from the 3'-poly(A) tract and extending to within 5 nucleotides of the termination codon. Two other RNA fragments of 21 and 25 nucleotides in length arise from the 5'-non-coding region of the message and possess an AUG-sequence at their 3'-termini which is the initiation codon. The presence of distinct by homologous sequences in several sets of large RNA fragments is consistent with the presence of several closely related protamine mRNA's. (+info)
Sites of in vivo histone methylation in developing trout testis.
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Specific lysyl residues of trout testis histones H3 and H4 are methylated partially during rainbow trout spermatogenesis. Histones H1, H2A, H2B, and protamine are not methylated. The single site (lysine 20) in histone H4 and the two major sites (lysines 9 and 27) in histone H3 are homologous to those determined for other organisms, but an additional minor site (lysine 4) occurs in histone H3. As described for calf thymus, both histones H3 and H4 contain epsilon-N-mono- and dimethyllysine, while histone H3 contains in addition, epsilon-N-trimethyllysine. The trout-specific histone H6, which accounts for 0.5 to 1.0% of total histone, contains a sequence for residues 3 to 5,-Arg-Lys-Ser-, which is the same as one methylated in histones H3, at lysines 9 and 27. However, histone H6 yields only trace amounts of [3H]methyl incorporation and no detectable methyllysines on amino acid analysis. (+info)
Histone methylation. Its occurrence in different cell types and relation to histone H4 metabolism in developing trout testis.
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Histone methylation in developing trout testis has been observed in the diploid stem cells and primary spermatocytes, which actively synthesize DNA and histones. In spermatids, histone methylation is minimal and so probably plays no role in the replacement of histones by protamine which is characteristic of this cell type. No turnover of histone methyl groups could be detected over several hours, so that unlike acetylation or phosphorylation of histones, methylation in this tissue appears to be a stable, irreversible modification. When histone H4, labeled with [14C]methyl groups, is separated on starch gels into acetylated and phosphorylated derivatives, [14C]methyl label does not appear in positions characteristic of newly synthesized histone H4, i.e. the highly acetylated (di-, tri-, and tetra-acetylated), unphosphorylated species. [14C]Methyl label appears rather in the unphosphorylated, and unacetylated or monoacetylated species, shifting with time to the monophosphorylated form of histone H4. These data suggest a temporal sequence of events for histone H4: synthesis, then acetylation and deacetylation, followed by methylation and phosphorylation. Occurring late after histone synthesis and assembly into chromatin, histone methylation might then be necessary for histone interactions with other molecules (e.g. histone phosphokinase) prior to mitosis. (+info)
A model-based method for identifying species hybrids using multilocus genetic data.
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We present a statistical method for identifying species hybrids using data on multiple, unlinked markers. The method does not require that allele frequencies be known in the parental species nor that separate, pure samples of the parental species be available. The method is suitable for both markers with fixed allelic differences between the species and markers without fixed differences. The probability model used is one in which parentals and various classes of hybrids (F(1)'s, F(2)'s, and various backcrosses) form a mixture from which the sample is drawn. Using the framework of Bayesian model-based clustering allows us to compute, by Markov chain Monte Carlo, the posterior probability that each individual belongs to each of the distinct hybrid classes. We demonstrate the method on allozyme data from two species of hybridizing trout, as well as on two simulated data sets. (+info)
Relationship between individual variation in morphological characters and swimming costs in brook charr (Salvelinus fontinalis) and yellow perch (Perca flavescens).
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The objective of this study was to examine if individual variation in morphological characters is related to swimming costs in wild and domestic brook charr, and in wild yellow perch. Our results indicate that absolute swimming cost was higher in wild and domestic brook charr individuals having a stout body shape, and these individuals are therefore less efficient swimmers. These results are consistent with field observations that described relationships between individual variation in morphology and habitat use in salmonids. Further analyses indicated that standard metabolic rates were higher in individuals having a stout body shape, and that net swimming cost was not related to body shape. Accordingly, the higher swimming cost of stout individuals is probably an indirect consequence of an increase in standard metabolic rate. In wild yellow perch, absolute and net swimming costs were higher in individuals having a stout body shape and a low aspect caudal fin, and standard metabolic rate was not related to body shape. Therefore, in contrast to brook charr, individual variation in the swimming cost of yellow perch appears to be related to morphological characters that affect drag and thrust forces, which is consistent with previously published inter-specific observations. (+info)