Stroke and glide of wing-propelled divers: deep diving seabirds adjust surge frequency to buoyancy change with depth

In order to increase locomotor efficiency, breath-holding divers are expected to adjust their forward thrusts in relation to changes of buoyancy with depth. Wing propulsion during deep diving by Brünnich's guillemots (Uria lomvia) was measured in the wild by high-speed (32 Hz) sampling of surge (tail-to-head) and heave (ventral-to-dorsal) accelerations with bird-borne data loggers. At the start of descent, the birds produced frequent surges (3.2 Hz) during both the upstroke and the downstroke against buoyancy to attain a mean speed of 1.2-1.8 m s(-1) that was close to the expected optimal swim speed. As they descended deeper, the birds decreased the frequency of surges to 2.4 Hz, relaying only on the downstroke. During their ascent, they stopped stroking at 18 m depth, after which the swim speed increased to 2.3 m s(-1), possibly because of increasing buoyancy as air volumes expanded. This smooth change of surge frequency was achieved while maintaining a constant stroke duration (0.4-0.5 s), presumably allowing efficient muscle contraction.     

Three forms of GnRH in the brain and pituitary of the turbot, Scophthalmus maximus: immunological characterization and seasonal variation

Three forms of GnRH, chicken (c) GnRH-II, salmon (s) and seabream (sb) GnRH, were immunologically characterized in the brain and pituitary of turbot by ELISA. cGnRH-II and sGnRH were detected in the brain, while sbGnRH and sGnRH (but not cGnRH-II) were detected in the pituitary. In females, the levels of cGnRH-II in the turbot brain extracts increased from May to July, concomitant with an increase in oocyte diameter. In the pituitary, sbGnRH was found to be the dominant form, with levels 100-600-fold those of sGnRH. Both sGnRH and sbGnRH in the pituitary showed variation during the spawning season; sbGnRH increased from May to July and correlated with the increase in oocyte diameter, while sGnRH decreased. The overall patterns were the same for male turbot, although levels were generally lower. These findings suggest that sbGnRH could be controlling reproduction in the turbot. However, the seasonal variation in sGnRH indicates a potential physiological role in turbot reproduction. This study gives the first immunological indications that sbGnRH is present in the pituitary of a pleuronectiform fish, and will provide the basis for further studies on the endocrine regulation of reproduction in flatfish.     

Bacillus thuringiensis in fecal samples from greenhouse workers after exposure to B. thuringiensis-based pesticides

In a study of occupational exposure to Bacillus thuringiensis, 20 exposed greenhouse workers were examined for Bacillus cereus-like bacteria in fecal samples and on biomonitoring filters. Bacteria with the following characteristics were isolated from eight individuals: intracellular crystalline inclusions characteristic of B. thuringiensis, genes for and production of B. cereus enterotoxins, and positivity for cry11 as determined by PCR. DNA fingerprints of the fecal isolates were identical to those of strains isolated from the commercial products used. Work processes (i.e., spraying) correlated with the presence of B. thuringiensis in the fecal samples (10(2) to 10(3) CFU/g of feces). However, no gastrointestinal symptoms correlated with the presence of B. thuringiensis in the fecal samples.     

Spermatogenesis and related plasma androgen levels in Atlantic halibut (Hippoglossus hippoglossus L.)

Spermatogenesis in male Atlantic halibut (Hippoglossus hippoglossus L.) was investigated by sampling blood plasma and testicular tissue from 15-39-month-old fish. The experiment covered a period in which all fish reached puberty and completed sexual maturation at least once. The germinal compartment in Atlantic halibut testis appears to be organized in branching lobules of the unrestricted spermatogonial type, because spermatocysts with spermatogonia were found throughout the testis. Spermatogenesis was characterized histologically, and staged according to the most advanced type of germ cell present: spermatogonia (Stage I), spermatogonia and spermatocytes (Stage II), spermatogonia, spermatocytes and spermatids (Stage III), spermatogonia, spermatocytes, spermatids and spermatozoa (Stage IV), and regressing testis (Stage V). Three phases could be distinguished: first, an initial phase with low levels of circulating testosterone (T; quantified by RIA) and 11-ketotestosterone (11-KT; quantified by ELISA), spermatogonial proliferation, and subsequently the initiation of meiosis marked by the formation of spermatocytes (Stage I and II). Secondly, a phase with increasing T and 11-KT levels and with haploid germ cells including spermatozoa present in the testis (Stage III and IV). Thirdly, a phase with low T and 11-KT levels and a regressing testis with Sertoli cells displaying signs of phagocytotic activity (Stage V). Circulating levels of 11-KT were at least four-fold higher than those of T during all stages of spermatogenesis. Increasing plasma levels of T and 11-KT were associated with increasing testicular mass throughout the reproductive cycle. The absolute level of, or the relation between, testis growth and circulating androgens were not significantly different in first time spawners compared to fish that underwent their second spawning season. These results provide reference levels for Atlantic halibut spermatogenesis.     

The patchwork nature of rolling-circle plasmids: comparison of six plasmids from two distinct Bacillus thuringiensis serotypes

Bacillus thuringiensis, the entomopathogenic bacteria from the Bacillus cereus group, harbors numerous extrachromosomal molecules whose sizes vary from 2 to more than 200kb. Apart from the genes coding for the biopesticide delta-endotoxins located on large plasmids, little information has been obtained on these plasmids and their contribution to the biology of their host. In this paper, we embarked on a detailed comparison of six small rolling-circle replicating (RCR) plasmids originating from two major B. thuringiensis strains. The complete nucleotide sequences of plasmid pGI1, pGI2, pGI3, pTX14-1, pTX14-2, and pTX14-3 have been obtained and compared. Replication functions, comprising, for each plasmid, the gene encoding the Rep-protein, double-strand origin of replication (dso), single-strand origin of replication (sso), have been identified and analyzed. Two new families, or homology groups, of RCR plasmids originated from the studies of these plasmids (Group VI based on pGI3 and Group VII based on pTX14-3). On five of the six plasmids, loci involved in conjugative mobilization (Mob-genes and origin of transfer (oriT)) were identified. Plasmids pTX14-1, pTX14-2, and pTX14-3 each harbor an ORF encoding a polypeptide containing a central domain with repetitive elements similar to eukaryotic collagen (Gly-X-Y triplets). These genes were termed bcol for Bacillus-collagen-like genes.     

Evaluation of five different cDNA labeling methods for microarrays using spike controls

Background

Several different cDNA labeling methods have been developed for microarray based gene expression analysis. We have examined the accuracy and reproducibility of such five commercially available methods in detection of predetermined ratio values from target spike mRNAs (A. thaliana) in a background of total RNA. The five different labeling methods were: direct labeling (CyScribe), indirect labeling (FairPlay? – aminoallyl), two protocols with dendrimer technology (3DNA^® Array 50? and 3DNA^® submicro?), and hapten-antibody enzymatic labeling (Micromax? TSA?). Ten spike controls were mixed to give expected Cy5/Cy3 ratios in the range 0.125 to 6.0. The amounts of total RNA used in the labeling reactions ranged from 5 – 50 μg.

Results

The 3DNA array 50 and CyScribe labeling methods performed best with respect to relative deviation from the expected values (16% and 17% respectively). These two methods also displayed the best overall accuracy and reproducibility. The FairPlay method had the lowest total experimental variation (22%), but the estimated values were consistently higher than the expected values (36%). TSA had both the largest experimental variation and the largest deviation from the expected values (45% and 48% respectively).

Conclusion

We demonstrate the usefulness of spike controls in validation and comparison of cDNA labeling methods for microarray experiments.

     

Intracellular infection with Spironucleus barkhanus (Diplomonadida: Hexamitidae) in farmed Arctic char Salvelinus alpinus

A case of intracellular systemic infection with the diplomonad flagellate Spironucleus barkhanus in farmed Arctic char Salvelinus alpinus is described. The parasites were widely disseminated throughout the vasculature and in most organs. Aggregates of the parasites were seen within well-defined structures regarded as host cells in capillaries and sinusoids of the liver, spleen and head kidney. Intracellular infection with Spironucleus spp. has never previously been reported. The prevalence of infection and mortality in the affected farm was low. In contrast to systemic spironucleosis in farmed Atlantic salmon, and despite huge numbers of flagellates in the vasculature, the tissues of the organs were remarkably unaffected. The relatively few gross and histopathological lesions may indicate that Arctic char are more tolerant to this parasite than Atlantic salmon.     

Modelling spatial dynamics of fish

Our ability to model spatial distributions of fish populations is reviewed by describing the available modelling tools. Ultimate models of the individual's motivation for behavioural decisions are derived from evolutionary ecology. Mechanistic models for how fish sense and may respond to their surroundings are presented for vision, olfaction, hearing, the lateral line and other sensory organs. Models for learning and memory are presented, based both upon evolutionary optimization premises and upon neurological information processing and decision making. Functional tools for modelling behaviour and life histories can be categorized as belonging to an optimization or an adaptation approach. Among optimization tools, optimal foraging theory, life history theory, ideal free distribution, game theory and stochastic dynamic programming are presented. Among adaptation tools, genetic algorithms and the combination with artificial neural networks are described. The review advocates the combination of evolutionary and neurological approaches to modelling spatial dynamics of fish.     

EBNA2 Binds to Genomic Intervals Associated with Multiple Sclerosis and Overlaps with Vitamin D Receptor Occupancy

Epstein-Barr virus (EBV) is a non-heritable factor that associates with multiple sclerosis (MS). However its causal relationship with the disease is still unclear. The virus establishes a complex co-existence with the host that includes regulatory influences on gene expression. Hence, if EBV contributes to the pathogenesis of MS it may do so by interacting with disease predisposing genes. To verify this hypothesis we evaluated EBV nuclear antigen 2 (EBNA2, a protein that recent works by our and other groups have implicated in disease development) binding inside MS associated genomic intervals. We found that EBNA2 binding occurs within MS susceptibility sites more than expected by chance (factor of observed vs expected overlap [O/E] = 5.392-fold, p < 2.0e-05). This remains significant after controlling for multiple genomic confounders. We then asked whether this observation is significant per se or should also be viewed in the context of other disease relevant gene-environment interactions, such as those attributable to vitamin D. We therefore verified the overlap between EBNA2 genomic occupancy and vitamin D receptor (VDR) binding sites. EBNA2 shows a striking overlap with VDR binding sites (O/E = 96.16-fold, p < 2.0e-05), even after controlling for the chromatin accessibility state of shared regions (p <0.001). Furthermore, MS susceptibility regions are preferentially targeted by both EBNA2 and VDR than by EBNA2 alone (enrichment difference = 1.722-fold, p = 0.0267). Taken together, these findings demonstrate that EBV participates in the gene-environment interactions that predispose to MS.     

The Inotropic Effect of the Active Metabolite of Levosimendan,OR-1896, Is Mediated through Inhibition of PDE3 in Rat Ventricular Myocardium

Aims

We recently published that the positive inotropic response (PIR) to levosimendan can be fully accounted for by phosphodiesterase (PDE) inhibition in both failing human heart and normal rat heart. To determine if the PIR of the active metabolite OR-1896, an important mediator of the long-term clinical effects of levosimendan, also results from PDE3 inhibition, we compared the effects of OR-1896, a representative Ca²⁺ sensitizer EMD57033 (EMD), levosimendan and other PDE inhibitors.

Methods

Contractile force was measured in rat ventricular strips. PDE assay was conducted on rat ventricular homogenate. cAMP was measured using RII_epac FRET-based sensors.

Results

OR-1896 evoked a maximum PIR of 33±10% above basal at 1 μM. This response was amplified in the presence of the PDE4 inhibitor rolipram (89±14%) and absent in the presence of the PDE3 inhibitors cilostamide (0.5±5.3%) or milrinone (3.2±4.4%). The PIR was accompanied by a lusitropic response, and both were reversed by muscarinic receptor stimulation with carbachol and absent in the presence of β-AR blockade with timolol. OR-1896 inhibited PDE activity and increased cAMP levels at concentrations giving PIRs. OR-1896 did not sensitize the concentration-response relationship to extracellular Ca²⁺. Levosimendan, OR-1896 and EMD all increased the sensitivity to β-AR stimulation. The combination of either EMD and levosimendan or EMD and OR-1896 further sensitized the response, indicating at least two different mechanisms responsible for the sensitization. Only EMD sensitized the α₁-AR response.

Conclusion

The observed PIR to OR-1896 in rat ventricular strips is mediated through PDE3 inhibition, enhancing cAMP-mediated effects. These results further reinforce our previous finding that Ca²⁺ sensitization does not play a significant role in the inotropic (and lusitropic) effect of levosimendan, nor of its main metabolite OR-1896.