Feed intake as explanation for density related growth differences of common sole Solea solea

Growth of common sole Solea solea is negatively correlated to density, which affects productivity in culture and hence commercial success. Studies of individual feed intake were performed to examine growth and population dynamics at different densities. Three initial stocking densities: 1.0, 2.1 and 3.9 kg m^?2 of individually tagged sole, referred to as low density (LD), medium density and high density HD), were examined during 145 days. Despite that tank productivity (g m^?2 day^?1), was highest for the HD group, the specific growth rate (SGR) decreased significantly with increase in stocking density. Individual size variation was similar between densities, indicating that growth was not associated with hierarchy and dominant behaviour. Individual data indicated that increased density reduced the growth potential of all individuals in a population. Individual feed intake was positively correlated to both fish size and individual SGR. Feed conversion ratio was likewise positively correlated to feed intake. The relative feed intake (g feed g fish^?1) was not correlated to fish size at any density tested, but was significantly highest for the LD population. This explains a substantial part of the better growth in the LD group supported by indications of better utilization of the ingested feed.     

PCR‐based identification of Pythium spp. causing cavity spot in carrots and sensitive detection in soil samples

On the basis of ITS sequences PCR primers were designed for the identification of the five Pythium species found to be most important for the development of carrot cavity spot in Norway: P. intermedium, P. sulcatum, P. sylvaticum, P. violae and P. ‘vipa’. The P. ‘vipa’ isolates had a unique ITS sequence, differed morphologically from all other Pythium isolates, and thus probably represent a new species. The PCR primers were species‐specific with no cross‐reaction to other Pythium species or to fungal isolates from carrot tested. The detection limits varied for the different primer pairs. The two most sensitive assays allowed detection of as little as 5 fg DNA. All five Pythium species could be detected in lesions from diseased carrots. Weak positive signals were obtained from some carrot samples without symptoms. PCR assays allowed detection of pathogens in soil. In samples of soil known to produce cavity spots on cropped carrots, strong signals were obtained. In several soil samples more than one of the five Pythium species could be detected. The utilization of this diagnostic PCR assay in analysis of field soil and carrot tissue might in the future be exploited to reduce the incidence of this serious carrot disease.     

What are the prospects for genetically engineered,disease resistant plants?

Insect and herbicide-resistant plants are the most widely grown transgenics in agricultural production. No strategy using genetically engineered plants for disease resistance has had a comparable impact. Why is this? What are the prospects for introducing transgenic disease resistant plants to agriculture? We review the biological background for strategies used to make disease resistant GM crops, illustrate examples of these different strategies and discuss future prospects.     

Accountability of experts in the Danish national park process

In 2002 the Danish Minister of Environment initiated a process to investigate the possibilities of establishing national parks in Denmark. For this purpose experts were mobilised to investigate the status and potentials of the areas in question.The national park process was extensive in scope and complex, and in theory such complexity is assumed to make it difficult for non-experts to understand all the relevant aspects of policy. This exclusion of non-experts may lead to scientification of politics. Furthermore politicisation of science might occur as experts might advocate political interests disguised as objective science, and policy-makers might select results that further their own interests. As a result policy-makers risk losing a source of legitimacy, scientists risk losing credibility and the citizens risk losing the possibility to hold policy-makers accountable for their decisions, which puts democracy at risk.This paper examines the accountability relationships that experts were a part of in the national park process. These include accountability towards the employer, towards the buyer and towards the general public. The purpose is to determine if these relationships were adequate to circumvent the problems associated with scientification of politics and to discuss how accountability relationships and thereby democracy could be strengthened.The empirical analysis shows that in the national park process experts were mainly accountable towards the National Forest and Nature Agency. There were formal accountability relationships between the experts and the local steering committees and the national advisory group, but these relationships were less significant. Moreover, despite the fact that the process was deemed unusually open to the public by the participants, the relationship between experts and the public cannot be characterised as an accountability relationship and could have been improved by including experts in the deliberative fora of the process.     

Plant Community and Target Species Affect Responses to Restoration Strategies

Increases in Kentucky bluegrass and smooth bromegrass on northern Great Plains rangelands have the potential to negatively impact ecosystem function, lower plant diversity, and alter seasonal forage distribution, but control strategies are lacking in the region. A project was initiated on a heavily invaded 16-ha grassland that had not been grazed or hayed for at least 20 yr. Five restoration treatments and a control were initiated in 2003 on communities dominated by 1) smooth bromegrass (Bromus inermis Leyss.), 2) Kentucky bluegrass (Poa pratensis L.), 3) warm-season native grasses, 4) a mix of introduced species, and 5) smooth bromegrass and Kentucky bluegrass. Restoration treatments were 1) late-April burn, 2) late-April burn followed by imazapic at 511.62 mL ai · ha^?1, 3) imazapic only at the same rate, 4) mowing, 5) mowing followed by litter removal, and 6) control. We found that treatment responses were affected by target species, community category, and year. Generally, burning followed by the herbicide imazapic reduced Kentucky bluegrass in the species composition, but smooth brome was reduced by mowing followed by raking. Burning followed by imazapic reduced live grass biomass in all community categories except the native the year following treatment, but by the third year of the study live grass biomass was maintained across all treatments. In the third year of the study, responses of Kentucky bluegrass, other invasive species, and native grasses to restoration treatment differed depending on community. The use of burning plus imazapic was promising for control of Kentucky bluegrass but its use by producers may be limited by yield reductions in early years. Our data suggest management strategies should vary depending on whether the goal is to reduce one or several invaders, specific invader identity, and community type in which the invader is growing. We also found that the most effective strategy was an adaptive management approach, one where treatments are chosen in response to changes in community composition and depending on resource conditions.     

Evaluation of Serum and Seminal Plasma Markers in the Diagnosis of Canine Prostatic Disorders

Serum and seminal plasma concentrations or activities of acid phosphatase (AP), prostate specific antigen (PSA), and canine prostate specific esterase (CPSE) were measured in normal dogs, dogs with benign prostatic hyperplasia (BPH), dogs with bacterial prostatitis, and dogs with prostatic carcinoma to determine if these assays would be of value in differentiating dogs with prostatic carcinoma from normal dogs, and dogs with other prostatic disorders. In addition, tissue sections of prostatic adenocarcinomas were stained with antiprostatic AP, anti-CPSE, and anti-PSA antibodies to determine if these would be suitable immunohistochemical markers of prostatic carcinoma. Prostate-specific antigen was not detected in canine serum or seminal plasma. Serum and seminal AP activities did not differ significantly between normal dogs and those with prostatic diseases, or among dogs with different prostatic disorders. Serum CPSE activities were significantly higher in dogs with BPH than in normal dogs. Mean serum CPSE activities in dogs with BPH, bacterial prostatitis, and prostatic carcinoma were not significantly different from each other. Slight to moderate immunohistochemical staining of canine prostatic adenocarcinomas was noted for prostatic AP and PSA; most tumors did not stain for CPSE. These results show that proteins of prostatic origin appear in the serum of dogs as a result of prostatic pathology, especially BPH. Canine prostatic adenocarcinoma does not appear to be associated with significant increases in CPSE or AP activities, possibly because of down-regulation of these enzymes by prostatic carcinoma cells. It is also possible that failure to detect significant differences resulted from limited statistical power for some groups and pairwise analyses because of the small number of dogs evaluated.     

Immunoprophylaxis of bovine dermatophytosis.

The literature on immunoprophylaxis as control method for ringworm in cattle is reviewed. Scientific papers on immune response to dermatophyte antigens and vaccination against ringworm were obtained from personal files and computerized search in 4 relevant databases. Vaccines with antigens of Trichophyton verrucosum stimulate a humoral and cellular immune response. In animals vaccinated with inactivated vaccines, some protection is observed after challenge. However, the protective immunity is inadequate in most cases. Vaccination with live vaccines elicits an immune response that prevents the development of clinical disease. The protective immunity is based mainly on the cellular branch of the immune system. The efficacy and safety of live dermatophyte vaccines have been demonstrated in both challenge experiments and field trials from different countries. Effective control of ringworm in cattle has been achieved in regions implementing systematic vaccination.     

Characterization of Escherichia coli strains isolated from pigs with edema disease.

Escherichia coli strains belonging to serogroups O 138 and O 139 isolated from pigs with edema disease, were characterized with respect to the presence of genes encoding Shiga-like toxin I, Shiga-like toxin II and Shiga-like toxin IIv (SLT I, SLT II and SLT IIv). Genes coding for the heat-stable and heat-labile enterotoxins (ST I and LT I) were also detected. Plasmid profiling, restriction enzyme digestion of total DNA, and ribotyping were performed for further characterization of the strains. The oligonucleotide probes applied in this study appeared to be useful tools for detecting genes coding cytotoxins and enterotoxins. DNA from 12 of 16 strains hybridized with two SLT II probes, and DNA from two SLT IIv encoding strains also hybridized with the ST I probe. DNA from one SLT IIv negative strain hybridized with the LT I probe. The results from plasmid profiling, restriction enzyme digestion, and ribotyping were compared with serogrouping in attempts to distinguish between the different E. coli edema disease isolates. Fourteen different plasmid profiles were identified, and as restriction patterns barely did, and ribotyping patterns did not, reveal any information useful for differentiation of the strains beyond serogroup level, plasmid profiling seemed to be the most suitable method for discrimination between the edema disease strains investigated here.     

Kinetics of sodium channel modification as the basis for the variation in the nerve membrane effects of pyrethroids and DDT analogs

The effects of a wide range of pyrethroids and DDT analogs on the membrane potential and membrane sodium currents were studied in crayfish giant axons. Compounds differed greatly in their ability to produce depolarizing afterpotentials, repetitive firing, and membrane depolarization. The differences observed at the membrane potential level could be explained by differences in the kinetics with which the insecticides interact with the nerve membrane sodium channel. The compounds containing a cyano group at the α position retain sodium channels in a modified open state persistently, depolarize the membrane, and block the action potential without causing repetitive firing. The pyrethroids without an α-cyano group and DDT analogs retain sodium channels in a modified open state only transiently, cause large depolarizing afterpotentials, and evoke repetitive firing with minimal effect on the resting potential. The effects of the phenoxybenzyl pyrethroids were found to be intermediate between these two extremes suggesting that a continuous variation exists in kinetics with which pyrethroids and DDT analogs modify sodium channels. It was not necessary to assume a second site of action to account for the variability observed. The implications of these results to the construction of quantitative structure-activity relationships is discussed.