Zooplankton diversity and the predatory impact by larval and small juvenile fish at the Fisher Banks in the North Sea

The biomass and diversity of the mesozooplankton and fish larvaecommunity were investigated across a frontal zone in the centralNorth Sea in the early summer, to investigate whether larvalfish predation is a regulator of mesozooplankton production.Pronounced changes in the mesozooplankton community were observedacross the front off the Jutlandic coast. The biomass and thediversity of copepods changed across the front as the populationof Calanus finmarchicus became abundant in the deeper water.The crustaceans (Acartia spp. and Evadne spp.) and polychaetelarvae dominated the mesozooplankton in the coastal water. Thebiomass of fish larvae was dominated by gadoid larvae. As inthe copepods, a shift in fish diversity was observed in thefrontal zone. On the coastal side of the front, whiting (Merlangiusmerlangus) dominated the biomass, while offshore from the frontwhiting were absent and cod (Gadus morhua) was the dominantlarval fish species on the deeper stations. The present investigationdemonstrates two different trophic pathways related to hydrographyin the central North Sea. First, in the shallow coastal water,the abundant small neritic copepods are predominately predatedby whiting, while in the offshore region the larger oceaniccopepods are predated by cod larvae. However, the predationpressure by the fish larvae was in general low (<10%) relativeto copepod production per day. Consequently, in the early summer,the copepod production potentially results in a build-up ofcopepod biomass on both sides of the front.     

Production of an antiviral factor by murine spleen cells after treatment with Corynebacterium parvum.

We have previously shown that injection of Corynebacterium parvum (CP) in mice protected them against lethal encephalitis induced by herpes simplex virus, (HSV). It is shown here that spleen cells of CP-injected mice in vitro produce a factor capable of inhibiting the replication of HSV in mouse embryo fibroblasts (MEF). A similar activity was produced after in vitro exposure of spleen cells from untreated mice to CP. CP was only slightly mitogenic in contrast to phytohemagglutinin (PHA), concanavalin A (Con A), and bacterial lipopolysaccharide (LPS) which were strongly mitogenic but did not induce antiviral activity high enough to be detected in the HSV-MEF system. The activity produced by CP-treated spleen cells appeared to be interferon since it was trypsin sensitive and species specific and not virus specific, and since preincubation of the cells was required to demonstrate an antiviral effect. However, the identity of CP-induced interferon with any of the previously described subclasses of interferon remains to be determined.     

Acute lindane poisoning with development of muscle necrosis.

A 35-year-old man ingested food contaminated with lindane, an insecticide containing almost pure gamma hexachlorocyclohexane. Grand mal seizures and severe acidemia developed rapidly. The seizures recurred for nearly 2 hours, then ceased. In addition, the patient had muscle weakness and pain, headaches, episodic hypertension, myoglobinuria, acute renal failure and anemia. Pancreatitis developed 13 days after the ingestion of lindane. A muscle biopsy on the 15th day of illness demonstrated widespread necrosis and regeneration of muscle fibres. The patient''s condition improved and he was discharged 24 days after the onset of his illness. During the year following the poisoning the patient noted difficulty with recent memory, loss of libido and easy fatigability. One year after lindane ingestion the results of physical examination, including those for muscle power and bulk, were normal.     

Detection of Bacillus thuringiensis kurstaki HD1 on cabbage for human consumption

The objectives of the study were to develop a specific procedure for quantification and identification of Bacillus thuringiensis kurstaki HD1, which is used as a biopesticide, and to quantify its presence in different kinds of cabbage for human consumption. We found that B. thuringiensis kurstaki HD1 can be distinguished from other B. thuringiensis strains by its unique random amplification of polymophic DNA-PCR pattern with the OPA9 primer and the presence of the flagellin genes, as detected by the primers FLAB1 and FLAB2. We detected from one to 100 Bacillus cereus-like bacteria in 10 batches of five different cabbage products for consumption. As many as 73 out of 134 isolates (53.7%) were identical with B. thuringiensis kurstaki HD1. The results show that B. thuringiensis kurstaki HD1 from biopesticides can be found in vegetables for human consumption.     

Change in suicide rates for patients with schizophrenia in Denmark, 1981-97: nested case-control study

Objective To study the change in risk of suicide among patients with schizophrenia and related disorders.Design Nested case-control design with linked data.Setting 4 longitudinal Danish registers.Participants 18 744 people aged up to 75 years who committed suicide in 1981-97 individually matched with 20 controls.Results Over the time studied the reduction in suicide rate among patients with schizophrenia and schizophrenia spectrum disorder was similar to that seen in the general population (incidence rate ratio 1.00, 95% confidence interval 0.98 to 1.03). The reduction among patients with other psychosis in the schizophrenia spectrum was faster than the reduction seen in the general population. Among people admitted to hospital with schizophrenia the risk of suicide was highest in the first year after first admission, and the excess risk was largest in the younger age groups—that is, the risk decreased per year for every additional year of age.Conclusion The suicide rate among patients with a diagnosis of schizophrenia and related disorders has fallen. This may be due to better psychiatric treatment, reduced access to means of suicide, or improvements in treatment after suicide attempts.     

Mapping the spawning grounds of North Sea cod (Gadus morhua) by direct and indirect means

Despite recent evidence for sub-stock structuring, North Sea cod are assessed as a single unit. As a consequence, knowledge of sub-stock trends is poor. In particular, there are no recent evaluations of which spawning grounds are active. Here we report results from the first ichthyoplankton survey to cover the whole North Sea. Also, this survey, conducted in 2004, was the first to make extensive use of DNA-based molecular methods to unambiguously identify early developmental stage cod eggs. We compare the findings from the plankton survey with estimated egg production inferred from the distribution of mature cod in contemporaneous trawl surveys. Results from both approaches were in general agreement and showed hot spots of egg production around the southern and eastern edges of the Dogger Bank, in the German Bight, the Moray Firth and to the east of the Shetlands. These areas broadly coincide with known spawning locations from the period 1940 to 1970. We were, however, unable to directly detect significant numbers of cod eggs at the historic spawning ground off Flamborough (northeast coast of England). The results demonstrate that most of the major spawning grounds of cod in the North Sea are still active but that some localized populations may have been reduced to the point where it is now difficult to detect the presence of eggs in the plankton.     

Disruption of the Pseudomonas aeruginosa Tat system perturbs PQS-dependent quorum sensing and biofilm maturation through lack of the Rieske cytochrome bc1 sub-unit

Extracellular DNA (eDNA) is a major constituent of the extracellular matrix of Pseudomonas aeruginosa biofilms and its release is regulated via pseudomonas quinolone signal (PQS) dependent quorum sensing (QS). By screening a P. aeruginosa transposon library to identify factors required for DNA release, mutants with insertions in the twin-arginine translocation (Tat) pathway were identified as exhibiting reduced eDNA release, and defective biofilm architecture with enhanced susceptibility to tobramycin. P. aeruginosa tat mutants showed substantial reductions in pyocyanin, rhamnolipid and membrane vesicle (MV) production consistent with perturbation of PQS-dependent QS as demonstrated by changes in pqsA expression and 2-alkyl-4-quinolone (AQ) production. Provision of exogenous PQS to the tat mutants did not return pqsA, rhlA or phzA1 expression or pyocyanin production to wild type levels. However, transformation of the tat mutants with the AQ-independent pqs effector pqsE restored phzA1 expression and pyocyanin production. Since mutation or inhibition of Tat prevented PQS-driven auto-induction, we sought to identify the Tat substrate(s) responsible. A pqsA::lux fusion was introduced into each of 34 validated P. aeruginosa Tat substrate deletion mutants. Analysis of each mutant for reduced bioluminescence revealed that the primary signalling defect was associated with the Rieske iron-sulfur subunit of the cytochrome bc₁ complex. In common with the parent strain, a Rieske mutant exhibited defective PQS signalling, AQ production, rhlA expression and eDNA release that could be restored by genetic complementation. This defect was also phenocopied by deletion of cytB or cytC₁. Thus, either lack of the Rieske sub-unit or mutation of cytochrome bc₁ genes results in the perturbation of PQS-dependent autoinduction resulting in eDNA deficient biofilms, reduced antibiotic tolerance and compromised virulence factor production.     

Isolation and taxonomic affiliation of N-heterocyclic aromatic hydrocarbon-transforming bacteria

The azaarenes (nitrogen-containing heterocyclic aromatic hydrocarbons) are products of incomplete combustion processes and thus are widely distributed with tar and oil products in the environment. Despite their adverse organoleptic, toxic, and carcinogenic characteristics, the biodegradability and fate of multi-ring azaarenes have received little attention. This work demonstrates the presence of genetically diverse azaarene-degrading bacteria in coal tar-contaminated soils. Thirty-eight bacterial strains able to transform the three-ring azaarenes, 5,6- and 7,8-benzoquinoline, phenanthridine, phenazine, or acridine, were isolated. Only seven of these strains grew in liquid medium on the specific azaarene compounds on which they were isolated using plates; and the rest transformed the azaarenes without growth. Taxonomic characterization by 16S ribosomal DNA sequencing revealed that our enrichment technique provided a diversity of 18 different azaarene-transforming bacterial species. Only a few strains were able to mineralize the homocyclic analogue, phenanthrene. Several of the isolates, e.g., Dyadobacter fermentans, Methylopila capsulata, and Agrobacterium tumefaciens, were related to genera relatively unknown with respect to the biodegradation of xenobiotic compounds. These strains can provide further information on the fate of azaarenes in the environment.     

The mouse as a model for heart morphogenesis in mammals: the origin of myocytes and studies with cardiac explants

The heart is one of the first organs to form during embryogenesis since its circulatory function is critical from early stages for embryo survival. In man, morphological events are affected by molecular perturbations, which can lead to a congenital heart defect. It is important therefore to understand not only the molecular signals, but also the morphological events, which govern myocardial cell identity. The study of transgenic mouse lines, Mlc1v-nlacZ-24 and Mlc3f-nlacZ-2, has led to the identification of a new precardiac territory, the anterior heart field, which has also been described recently in birds, and which contributes to the myocardium of the arterial pole of the heart. The use of explant cultures also indicates that pharyngeal mesoderm participates in the formation of the outflow tract and right ventricle and shows that the primitive heart tube has a predominantly left ventricular identity. We have also shown that Fgf-10 is expressed in the anterior heart field, where a role for FGF signaling in arterial pole morphogenesis is suggested by inhibitor experiments. Finally explant cultures have been employed to examine the acquisition of left-right atrial identity. The Mlc3f-nlacZ-2 line, which marks the right atrium, allowed us to determine the time window during which left-right signaling confers left-right atrial identity.     

Helicobacter pylori: an invading microorganism? A review

In this review we evaluate the pros and cons of Helicobacter pylori invasion of epithelial cells as part of the natural history of H. pylori infection. H. pylori is generally considered an extracellular microorganism. However, a growing body of evidence supports the controversial hypothesis that at least a subset of H. pylori microorganisms has an intracellular (intraepithelial) location. Most significant is the fact that H. pylori invades cultured epithelial cells with invasion frequencies similar to Yersinia enterocolitica and better than Shigella flexneri; furthermore, studies of invasion mechanisms suggest that H. pylori invasion of and survival within epithelial cells is not merely a passive event, but requires active participation of the microorganism. Although many studies of human gastric biopsy specimens have failed to demonstrate any intracellular H. pylori, some studies have revealed a minor fraction of H. pylori inside gastric epithelial cells, with possible linkage to peptic ulceration and epithelial cell damage. In conclusion, these data encourage further research to establish whether intracellular H. pylori does play a role in H. pylori colonization of the human stomach and in peptic ulcer pathogenesis.