The authors present the results of an epidemiological surveillance programme involving Atlantic salmon (Salmo salar) populations in north-eastern Spain. The study investigates the risk factors ...critical in disease transmission, which include the presence of potentially pathogenic micro-organisms, the innate cell-mediated immune response of the salmon, and the potential interactions between the two. Also taken into account are the biological and migratory cycles of these salmon populations. The results showed that Aeromonas salmonicida and Saprolegnia parasitica were the micro-organisms that played the most important role in the transmission of the disease by virtue of their pathological characteristics, their occurrence in large numbers, and their capacity to transmit disease. With regard to the cell-mediated immune response, the authors observed a wide variability between individuals in some cell groups, as well as certain seasonal and age differences. These may be factors that predispose the animals to infection or to becoming asymptomatic carriers, with the attendant risk of transmitting infection in the course of migration. This could be especially relevant in the case of salmon infected with A. salmonicida and S. parasitica, since it has been observed that such salmon have a decreased number of leucocytes compared to non-infected salmon.
Ion channel mapping techniques are described and the results for two fungal organisms,Saprolegnia feraxandNeurospora crassa, are presented. In these species, two channel types have been ...characterized, stretch-activated channels exhibiting significant calcium permeability and spontaneous channels having significant potassium permeability. Two distinct analyses of patch clamp data, analysis of channel self-clustering and association between different channel types, and localization along the hyphae, reveal significant differences between the two organisms.S. feraxmaintains a tip-high gradient of both channel types which is lost after disruption of the actin cytoskeleton. There is significant self-clustering of the channels, as well as interactions between channel types.N. crassaon the other hand does not maintain tip-high gradients, and clustered distributions are observed only for the stretch-activated channels. In terms of physiological roles, evidence is quite strong that the stretch-activated channels function as a growth sensor inS. ferax, but have an unknown function inN. crassa. In both organisms, the potassium permeable channels presumably function in potassium uptake. The differences between these two organisms may be due, in part, to differences in their normal environment: aquatic versus terrestrial.
Long-chain n-3 PUFAs (polyunsaturated fatty acids) such as EPA (eicosapentaenoic acid; 20:5 n-3) have important therapeutic and nutritional benefits in humans. In plants, cyanobacteria and nematodes, ...omega3-desaturases catalyse the formation of these n-3 fatty acids from n-6 fatty acid precursors. Here we describe the isolation and characterization of a gene ( sdd17 ) derived from an EPA-rich fungus, Saprolegnia diclina, that encodes a novel omega3-desaturase. This gene was isolated by PCR amplification of an S. diclina cDNA library using oligonucleotide primers corresponding to conserved regions of known omega3-desaturases. Expression of this gene in Saccharomyces cerevisiae, in the presence of various fatty acid substrates, revealed that the recombinant protein could exclusively desaturate 20-carbon n-6 fatty acid substrates with a distinct preference for ARA (arachidonic acid; 20:4 n-6), converting it into EPA. This activity differs from that of the known omega3-desaturases from any organism. Plant and cyanobacterial omega3-desaturases exclusively desaturate 18-carbon n-6 PUFAs, and a Caenorhabditis elegans omega3-desaturase preferentially desaturated 18-carbon PUFAs over 20-carbon substrates, and could not convert ARA into EPA when expressed in yeast. The sdd17 -encoded desaturase was also functional in transgenic somatic soya bean embryos, resulting in the production of EPA from exogenously supplied ARA, thus demonstrating its potential for use in the production of EPA in transgenic oilseed crops.
The ability of five monoclonal antibodies (Mabs) raised against a pathogenic
Saprolegnia parasitica isolate from brown trout to detect and differentiate between isolates with bundles of long hairs (
...S. parasitica) and other
Saprolegnia species was determined by means of an indirect immunofluorescence assay. Four of the Mabs used recognized some of the long-haired
S. parasitica isolates but also cross-reacted with other
Saprolegnia species without bundles of hairs and with
Achlya sp. The other Mab (named 18A6) was able to differentiate between the asexual and most of the sexual isolates in the group of long-haired
S. parasitica isolates, but did not recognize
Achlya sp. or the
Saprolegnia species without bundles of hairs, with the exception of
S. hypogyna. These results indicate that isolates with bundles of long hairs are closely related with other members of genus
Saprolegnia and share several antigens. However, Mab 18A6 seems to recognize an epitope that is expressed mainly in the asexual isolates in the long-haired
S. parasitica isolates.
In late June 2013, because of sudden and unjustified increase in mortality of apparent healthy fish in Hasanloo dam cage culture, random sampling was convicted from a live dying and dead fishes. ...Forty fishes (20 alive and 20 dead fishes) from two cage with the weight of 200-300 gr were sampled. Samples were sent to private factor laboratory ice pieces for evolution. Some physicochemical parameters of Hasanloo dam water including nitrite, nitrate, ammonium, soluble solid materials, temperature, dissolved oxygen and pH was measured. To investing the probability of bacterial, fungal and parasitic discover outbreaks sample were taken from the kidney, gills and skin of fish. The result of different investing revealed the presence of algal bloom, oxygen shortage, executive problems and fishing net fountain obstruction due to accumulation of planktons and suspended material. Because of increase in light intensity, nutritive substances level, warming of water temperature and static suability of water hydrological status, algal blooming had occurred in Hasanloo dam that not only destroyed the gills of fish but also created competition for soluble oxygen at night with some phytoplankton species causing hypoxia and death of salmon in the breeding farm. The result of general bacterial cutler was negative and mild secondary infection with S aprolegnia species was detected in PGYEA culture. The result of liver histopathology indicated the presence of hepatic ceroidosis because of non-standard diets with high levels of carbohydrates. Gill blade inflammation and hyperplasia was the observed. Due to high amounts of ionized ammonia among culture nets resolving from summer mortality syndrome.
Artificial infection with the fungi Saprolegnia diclina BKKU 0506 and Achlya bisexualis BKKU 0616 was induced in the platyfish (Xiphophorus maculates) via exposure to zoospores following artificial ...injury by scale removal and net-shake or “ami-momi” treatment. The results suggested that ami-momi treatment, but not scale removal, could be used to establish severe fungal infection in small freshwater tropical fish as well as salmonids.
ABSTRACT
The distribution of organelles and microtubules in hyphal tips of the oomycete, Saprolegnia feras, were quantitatively determined at high resolution from serial-section electron microscopy ...of freeze-substituted cells. All the organelles and the microtubules were non-uniformly distributed, each showing a characteristic longitudinal gradient starting at a different point behind the tip. In addition, when the cytoplasmic cross-sectional area was divided into radial regions, all organelles occurred preferentially in either the central (mitochondria and Golgi bodies) or the peripheral (microtubules, wall vesicles and spherical vesicles) region. The nuclei were so large as to span both regions but were always oriented with their centrioles facing the plasmalemma. Microtubules occurred in the extreme tips, became more abundant sub-apically, were predominantly short but increased in mean length with distance from the tip. The correlated patterns of organelle and cytoskeleton organization from this and previous work show that neither the microtubules nor the detected arrays of actin are sufficient to account for most organelle arrangements. However, on the basis of the distribution and orientation of the predominantly elongated wall vesicles, we suggest that the wall vesicles travel radially from their origin at the centrally located Golgi bodies to the cell periphery where they are transported longitudinally to the hyphal tip in conjunction with the plasmalemma-associated actin cables. Our data also suggest that the hyphae contain a cortical ectoplasm with which the nuclei interact, at least in part, via their centrioles and centriole-associated microtubules, and whose mechanical integrity is increased by both the peripheral actin cables and a high density of microtubules. We suggest that the endoplasm is less strong and has physiological properties that enhance the differentiation of endoplasmic reticulum and nuclear envelope into Golgi body production.
Epizootics of saprolegniasis occurred in 20 to 60 g freshwater-cultured coho salmon (Oncorhynchus kisutch) in Miyagi Prefecture, Japan. Cotton-like mycelia occurred on the body surface of infected ...fish, especially around the head, the adipose fin and the caudal fin, and aseptate hyphae occurred in the lesions. The hyphae also penetrated into the muscle and blood vessels. The isolated fungus was identified by asexual morphological characteristics as Saprolegnia parasitica (syn. S. diclina Type 1), a known salmonid fish pathogen.
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