Action spectra of microalgal photosynthesis and depth distribution of spectral scalar irradiance in a coastal marine sediment of Limfjorden, Denmark

The role of complementary spectral utilization of light for the zonation of different groups of oxygenic phototrophic organisms in sediments was studied. The marine sediment was covered by a dense population of diatoms with an underlying population of cyanobacteria. Action spectra for photosynthesis and spectral scalar irradiance, E₀, were measured directly in the sediment at a spatial resolution of 0.1 mm by the use of oxygen and light microsensors. The action spectrum for the diatoms was similar to the attenuation spectrum of the scalar irradiance, K₀, in the diatom layer with Chl.a. and carotenoids being the major photosynthetic pigments. The action spectrum of the cyanobacteria showed photosynthesis maxima at the absorption regions of Chl.a. and phycocyanin. The measured depth distribution of spectral scalar irradiance and the action spectra of diatoms and cyanobacteria were used to calculate the spectral quality for photosynthesis of the 400–700 nm light to which the two populations were exposed. This spectral quality was compared to that of the light incident on the sediment surface. Due to preferential extinction of wavelengths, at which their photosynthetically active pigments had maximal absorption, the relative light quality for diatoms was reduced to 85% of the quality of d incident light at a similar total quantum flux. This effect was partly due to spectral alterations of light backscattered from the underlying sediment with cyanobacteria. The cyanobacteria at the bottom of the euphotic zone, in contrast, experienced a light spectrum which was favorably altered, to 10% in quality, due to absorption by the overlying diatoms. It was concluded that these changes in spectral light quality can be considered as only one of more factors explaining the zonation of the two phototrophic populations, and that total light intensity and the chemical microenvironment are probably more important factors.     

Reproductive effort in Danish mudsnails (Hydrobiidae)

Summary The four species of Hydrobiid mudsnails found in Danish brackish water habitats are ranked with respect to reproductive effort. The biology of the species indicate that Hydrobia neglecta and Potamopyrgus jenkinsi, showing the highest reproductive effort are also more r-selected than the other species, H. ventrosa and H. ulvae.     

Septin9 is involved in T-cell development and CD8+ T-cell homeostasis

SEPTIN9 (SEPT9) is a filament-forming protein involved in numerous cellular processes. We have used a conditional knock out allele of Sept9 to specifically delete Sept9 in T-cells. As shown by fluorescence-activated cell sorting, loss of Sept9 at an early thymocyte stage in the thymus results in increased numbers of double-negative cells indicating that SEPT9 is involved in the transition from the double-negative stage during T-cell development. Accordingly, the relative numbers of mature T-cells in the periphery are decreased in mice with a T-cell-specific deletion of Sept9. Proliferation of Sept9-deleted CD8⁺ T-cells from the spleen is decreased upon stimulation in culture. The altered T-cell homeostasis caused by the loss of Sept9 results in an increase of CD8⁺ central memory T-cells.     

Anti‐hypertensive treatment preserves appetite suppression while preventing cardiovascular adverse effects of tesofensine in rats

Objective:

Tesofensine is a novel triple monoamine reuptake inhibitor which is in development for the treatment of obesity. Preclinical and clinical data suggest that appetite suppression is an important mechanism by which tesofensine exerts its robust weight reducing effect. Notably, the strong hypophagic response to tesofensine treatment is demonstrated to be linked to central stimulation of noradrenergic and dopaminergic neurotransmission. The sympathomimetic mode of action of tesofensine may also associate with the elevated heart rate and blood pressure observed in clinical settings, and we therefore sought experimentally to address this issue.

Design and Methods:

The anorexigenic and cardiovascular effects of tesofensine were studied simultaneously in telemetrized conscious rats in a combined real‐time food intake and cardiovascular telemetry monitoring system.

Results:

Acute administration of tesofensine caused a dose‐dependent hypophagic effect as well as increased heart rate and blood pressure. Interestingly, combined treatment with metoprolol (b₁ adrenoceptor blocker, 10‐20 mg/kg, p.o.) fully prevented the cardiovascular sympathetic effects of tesofensine while leaving the robust inhibitory efficacy on food intake unaffected. Similarly, the angiotensin AT₁ receptor antagonist telmisartan (1.0‐3.0 mg/kg, p.o.) did not interfere with the anti‐obesity effects of tesofensine, however, telmisartan only partially reversed the increase in systolic blood pressure and had no effect on the elevated heart rate induced by tesofensine.

Conclusion:

These data suggests that tesofensine causes elevations in heart rate and blood pressure by increasing sympathetic activity, and that different adrenoceptor subtypes may be responsible for the anti‐obesity and cardiovascular effects of tesofensine.     

Identification of a soybean chloroplast DNA replication origin-binding protein

Replication of chloroplast DNA (ctDNA) in several plants and in Chlamydomonas reinhardii has been shown to occur by a double displacement loop (D-loop) mechanism and potentially also by a rolling circle mechanism. D-loop replication origins have been mapped in several species. Minimal replication origin sequences used as probes identified two potential binding proteins by southwestern blot analysis. A 28 kDa (apparent molecular weight by SDS-PAGE analysis) soybean protein has been isolated by origin sequence-specific DNA affinity chromatography from total chloroplast proteins. Mass spectrometry analysis identified this protein as the product of the soybean C6SY33 gene (accession number ACU14156), which is annotated as encoding a putative uncharacterized protein with a molecular weight of 25,897 Da, very near the observed molecular weight of the purified protein based on gel electrophoresis. Western blot analysis using an antibody against a homologous Arabidopsis protein indicates that this soybean protein is localized specifically in chloroplasts. The soybean protein shares some homology within a single-stranded DNA binding (SSB) domain of E. coli SSB and an Arabidopsis thaliana mitochondrial-localized SSB of about 21 kDa (mtSSB). However, the soybean protein induces a specific electrophoretic mobility shift only when incubated with a double-stranded fragment containing the previously mapped ctDNA replication oriA region. This protein has no electrophoretic mobility shift activity when incubated with single-stranded DNA. In contrast, the Arabidopsis mtSSB causes a mobility shift only with single-stranded DNA but not with the oriA fragment or with control dsDNA of unrelated sequence. These results suggest that the 26 kDa soybean protein is a specific origin binding protein that may be involved in initiation of ctDNA replication.     

Nras overexpression results in granulocytosis, T-cell expansion and early lethality in mice

NRAS is a proto-oncogene involved in numerous myeloid malignancies. Here, we report on a mouse line bearing a single retroviral long terminal repeat inserted into Nras. This genetic modification resulted in an increased level of wild type Nras mRNA giving the possibility of studying the function and activation of wild type NRAS. Flow cytometry was used to show a variable but significant increase of immature myeloid cells in spleen and thymus, and of T-cells in the spleen. At an age of one week, homozygous mice began to retard compared to their wild type and heterozygous littermates. Two weeks after birth, animals started to progressively lose weight and die before weaning. Heterozygous mice showed a moderate increase of T-cells and granulocytes but survived to adulthood and were fertile. In homozygous and heterozygous mice Gfi1 and Gcsf mRNA levels were upregulated, possibly explaining the increment in immature myeloid cells detected in these mice. The short latency period indicates that Nras overexpression alone is sufficient to cause dose-dependent granulocytosis and T-cell expansion.     

Blockade of PD-1/B7-H1 interaction restores effector CD8+ T cell responses in a hepatitis C virus core murine model

The impaired function of CD8(+) T cells is characteristic of hepatitis C virus (HCV) persistent infection. HCV core protein has been reported to inhibit CD8(+) T cell responses. To determine the mechanism of the HCV core in suppressing Ag-specific CD8(+) T cell responses, we generated a transgenic mouse, core(+) mice, where the expression of core protein is directed to the liver using the albumin promoter. Using a recombinant adenovirus to deliver Ag, we demonstrated that core(+) mice failed to clear adenovirus-LacZ (Ad-LacZ) infection in the liver. The effector function of LacZ-specific CD8(+) T cells was particularly impaired in the livers of core(+) mice, with suppression of IFN-gamma, TNF-alpha, and granzyme B production by CD8(+) T cells. In addition, the impaired CD8(+) T cell responses in core(+) mice were accompanied by the enhanced expression of the inhibitory receptor programmed death-1 (PD-1) by LacZ-specific CD8(+) T cells and its ligand B7-H1 on liver dendritic cells following Ad-LacZ infection. Importantly, blockade of the PD-1/B7-H1 inhibitory pathway (using a B7-H1 blocking antibody) in core(+) mice enhanced effector function of CD8(+) T cells and cleared Ad-LacZ-infection as compared with that in mice treated with control Ab. This suggests that the regulation of the PD-1/B7-H1 inhibitory pathway is crucial for HCV core-mediated impaired T cell responses and viral persistence in the liver. This also suggests that manipulation of the PD-1/B7-H1 pathway may be a potential immunotherapy to enhance effector T cell responses during persistent HCV infection.     

The potential of optimizing prehospital triage of patients with suspected acute myocardial infarction using high-sensitivity cardiac troponin T and copeptin

Purpose: In patients with a suspected acute myocardial infarction (AMI), to evaluate the potential for early triage based on measurement of high-sensitivity cardiac troponin T (hs-cTnT) and copeptin in blood samples collected in the prehospital phase.

Materials and methods: In this retrospective study, we measured hs-cTnT and copeptin in blood samples collected in the ambulance form 962 patients with suspected AMI. The diagnostic accuracy was estimated by receiver-operating characteristic (ROC) curve area under the curve (AUC) for both biomarkers and a combined model. Multivariable Cox regression modelling was used to estimate the predictive value of both biomarkers.

Results: In total, 178 (19%) cases had AMI. The AUC for hs-cTnT was 0.81. Adding copeptin increased the AUC to 0.85 (p?=?0.004) and the combined model allowed a prehospital rule-out of 45% of cases without AMI (negative predictive value, NPV 98%). Both biomarkers are highly predictive of outcome.

Conclusions: A future application of hs-cTnT and copeptin measurement, performed already in the prehospital phase, could potentially improve the prehospital diagnostic and prognostic classification of patients with a suspected AMI.     

Deregulated Nras Expression in Knock-In Animals Harboring a Gammaretroviral Long Terminal Repeat at the Nras/Csde1 Locus

To investigate mechanisms and phenotypic effects of insertional mutagenesis by gammaretroviruses, we have developed mouse lines containing a single Akv 1-99 long terminal repeat (LTR) and a floxed PGK/Tn5 neomycin cassette at the Nras proto-oncogene at positions previously identified as viral integration sites in Akv 1-99 induced tumors. The insert did not compromise the embryonic development, however, the cassette had an effect on Nras expression in all tissues analyzed. Cre-mediated excision of the PGK/Tn5 neomycin cassette in two of the lines caused upregulation of Nras. Altogether, the knock-in alleles are characterized by modulation of expression of the target gene from more than ten-fold upregulation to three-fold downregulation and exemplify various mechanisms of deregulation by insertional mutagenesis. LTR knock-in mice may serve as a tool to investigate mechanisms of retroviral insertional mutagenesis and as a way of constitutive or induced modulation of expression of a target gene.