Carbon acquisition by diatoms

Diatoms are responsible for up to 40% of primary productivity in the ocean, and complete genome sequences are available for two species. However, there are very significant gaps in our understanding of how diatoms take up and assimilate inorganic C. Diatom plastids originate from secondary endosymbiosis with a red alga and their Form ID Rubisco (ribulose-1,5-bisphosphate carboxylase-oxygenase) from horizontal gene transfer, which means that embryophyte paradigms can only give general guidance as to their C acquisition mechanisms. Although diatom Rubiscos have relatively high CO₂ affinity and CO₂/O₂ selectivity, the low diffusion coefficient for CO₂ in water has the potential to restrict the rate of photosynthesis. Diatoms growing in their natural aquatic habitats operate inorganic C concentrating mechanisms (CCMs), which provide a steady-state CO₂ concentration around Rubisco higher than that in the medium. How these CCMs work is still a matter of debate. However, it is known that both CO₂ and HCO₃⁻ are taken up, and an obvious but as yet unproven possibility is that active transport of these species across the plasmalemma and/or the four-membrane plastid envelope is the basis of the CCM. In one marine diatom there is evidence of C₄-like biochemistry which could act as, or be part of, a CCM. Alternative mechanisms which have not been eliminated include the production of CO₂ from HCO₃⁻ at low pH maintained by a H⁺ pump, in a compartment close to that containing Rubisco.     

The relation of emotions to placebo responses

The hypothesis put forth is that expectations of treatment effects reduce negative emotions and thereby reduce symptoms, e.g. pain. Negative emotions increase pain, and it is hypothesized that placebos reduce pain by reducing negative emotions, i.e. feelings of nervousness, fear and anxiety. Placebo analgesia has been shown to be mediated via opioid activity, and relaxation increases opioid activity. The placebo acquires its relaxing effect due to verbal information that pain will be reduced, or due to associations between the placebo and the reduction in pain after effective treatment. Thus, the placebo signals that unpleasantness will be less after administration of the placebo. This involves negative reinforcement which is due to activation of a dopaminergic system that has been found to be activated during placebo analgesia and is involved in positive emotions. The nocebo effect of increased pain is, consistent with this model, because of increased fear and anxiety. The new aspect of the presented model is the hypothesis that expectations reduce negative emotions, and that negative reinforcement that involves the dopaminergic reinforcement system should be a contributor to placebo responses.     

MOBILIZATION OF β-1,3-GLUCAN AND BIOSYNTHESIS OF AMINO ACIDS INDUCED BY NH4+ ADDITION TO N-LIMITED CELLS OF THE MARINE DIATOM SKELETONEMA COSTATUM (BACILLARIOPHYCEAE)

Mobilization of the reserve β-1,3-glucan (chrysolaminaran) in N-limited cells of the marine diatom Skeletonema costatum (Grev.) Cleve (Bacillariophyceae) was investigated. The diatom was grown in pH-regulated batch cultures with a 14:10-h light:dark cycle until N depletion. In a pulse-chase experiment, the cells were first incubated in high light (200 μmol photons·m ^{− 2}·s ^{− 1}) with ¹⁴C-bicarbonate until dissolved inorganic carbon was exhausted. Unlabeled bicarbonate (1 mM) was then added, and the cells were incubated in the dark and subsequently in low light (20 μmol photons·m ^{− 2}·s ^{− 1}) with additions of 40 μM NH₄ ⁺ . In the ¹⁴C pulse phase with high light and N depletion, β-1,3-glucan accumulated and accounted for 85% of incorporated ¹⁴C. In the subsequent ¹⁴C chase phases, added NH₄ ⁺ was assimilated at an N-specific rate of 0.11 h ^{− 1} in both the dark and low light, and in both cases it caused a significant mobilization of β-1,3-glucan (dark, 26%; low light, 19%). Biochemical fractionation of organic ¹⁴C showed that free amino acids were most rapidly labeled in the early stage of NH₄ ⁺ assimilation, whereas proteins and polysaccharides were labeled more rapidly after 1.2 h. Analysis of the cellular free amino acids strongly indicated that de novo biosynthesis was occurring, with a Gln:Glu ratio increasing from 0.4 to 10 within 1.2 h. After the NH₄ ⁺ was exhausted, the cellular pools of glucan and amino acids became constant or slowly decreased. In another experiment, N-limited cells were first incubated in high light until dissolved inorganic carbon was exhausted and were further incubated in high light with 150 μM NH₄ ⁺ under inorganic carbon limitation. Added NH₄ ⁺ was assimilated at an N-specific rate of 0.023 h ^{− 1}, and cellular β-1,3-glucan decreased by 15% within 6 h. Hence, β-1,3-glucan was mobilized during NH₄ ⁺ assimilation, even though inorganic carbon was modifying the metabolic rates. The results provide new evidence of β-1,3-glucan supplying essential precursors for biosynthesis of amino acids and other components in S. costatum in both the dark and subsaturating light and even saturating light under inorganic carbon limitation.     

Transthoracic echocardiography for imaging of the different coronary artery segments: a feasibility study

Background

Cardiac resynchronisation therapy (CRT) improves mortality and morbidity in heart failure patients with wide QRS. Observational studies suggest that patients having more left ventricular dyssynchrony pre-implantation obtain greater benefit on ventricular function and symptoms with CRT.

Aim

To provide an analysis of the prevalence and type of dyssynchrony in patients included in the CARE-HF trial.

Methods

100 patients 67 (58 to 71) years were examined with echocardiography including tissue doppler imaging before receiving a CRT-pacemaker. Atrio-ventricular dyssynchrony (LVFT/RR) was defined as left ventricular filling time <40% of the RR-interval. Inter-ventricular mechanical delay (IVMD) was measured as the difference in onset of Doppler-flow in the pulmonary and aortic outflow tracts >40 ms. Intra-ventricular (regional) dyssynchrony in a 16-segment model was expressed either as a delayed longitudinal contraction (DLC) during the postsystolic phase or by tissue synchronisation imaging (TSI) with a predefined time-difference in systolic maximal velocities >85 ms.

Results

LVFT/RR was present in 34% and IVMD in 60% of patients while intra-ventricular dyssynchrony was present in 85% (DLC) and 86% (TSI) with a high agreement between the measures (Kappascore 0.86–1.00), indicating the methods being interchangeable. Patients with cardiomyopathy (53%) were more likely to have LVFT/RR <40% (45% vs. 21% (p= 0.02)) and more segments affected by intra-ventricular dyssynchrony 4(3, 5) vs. 3(1, 4), p = 0.002, compared to patients with ischemic heart disease.

Conclusion

The prevalence of intra-ventricular dyssynchrony is high in patients with heart failure, wide QRS and depressed systolic function. Most important, TSI appears to be a fast and reliable method to identify patients with intra-ventricular dyssynchrony likely to benefit from CRT.     

Changes in contraction‐induced phosphorylation of AMP‐activated protein kinase and mitogen‐activated protein kinases in skeletal muscle after ovariectomy

Recent evidence suggests that ovarian hormones contribute to altered function of skeletal muscle, however the signaling processes thought to regulate muscle function remain undefined in females. Thus, the purpose of this investigation is to determine if ovarian hormone status is critical for contraction‐induced activation of AMPK or MAPK in skeletal muscle. Female mice were divided into two groups, ovariectomy (OVX) and SHAM, which were then subjected to in situ isometric contractile protocols. AMPK, ERK 1/2, p38, and JNK phosphorylation were measured in the control and contracting limb. In the in situ protocol, OVX muscles were significantly more resistant to fatigue compared to the SHAM animals. In addition, the muscles from OVX mice demonstrated significantly lower levels of normalized AMPK phosphorylation at rest. AMPK phosphorylation was not increased in the muscles from SHAM mice after the in situ contractile protocol, while the OVX demonstrated significant increases in AMPK phosphorylation. After contraction, normalized ERK2 phosphorylation was significantly higher in the OVX group compared to the SHAM group. Both p38 and JNK phosphorylation increased in response to contraction; but no group differences were detected. A second set of SHAM and OVX animals were subjected to fatigue stimulated under in vitro conditions. Significant increases in AMPK and ERK2 phosphorylation were detected, but no differences were found between groups. In conclusion, removal of the ovaries results in different responses to contraction‐induced changes in phosphorylation of AMPK and ERK2 in female mice and suggests hormones secreted from the ovaries significantly impacts cellular signaling in skeletal muscle. J. Cell. Biochem. 107: 171–178, 2009. © 2009 Wiley‐Liss, Inc.     

Comparative aspects of infectious salmon anemia virus,an orthomyxovirus of fish,to influenza viruses

Infectious salmon anaemia (ISA) is a viral disease that was first recorded in 1984 in farmed Atlantic salmon. The infectious salmon anaemia virus (ISAV) is classified as the type species of the genus Isavirus in the Orthomyxoviridae family and is evolutionary remote to the influenza viruses. The genome consists of eight negative single-stranded RNA segments, and it utilises the same mechanisms as influenza viruses to enter and exit cells. Although a common ancestor of ISAV and other genera of Orthomyxoviruses could be dated back several millions of years, there are still many similarities between ISAV and the influenza viruses regarding morphology, replication cycles and interactions with their respective hosts.     

Association patterns and kinship in female reindeer (Rangifer tarandus) during rut

Non-random association of females has been reported in many social species, with kinship being the main mechanism in shaping these associations. Understanding the patterns of association during rut is particularly important in polygynous animals, as this may have implications for inbreeding vulnerability and genetic structuring of populations. However, these patterns are highly dynamic and may be influenced by the population sex ratio and male age structure. We examined females' association in reindeer (Rangifer tarandus), a highly polygynous ungulate, to determine whether genetically related females associate more often than non-kin during rut and whether this association was influenced by the aforementioned factors. During three rutting seasons the male age structure and the sex ratio of the herd was manipulated: two extremely female biased sex ratios, one with only adult males and one with only young males, whereas the third being closer to a more even sex ratio and male age structure. We found that genetic relatedness influenced female association in the mixed male age group, but not in the adult and young male age groups. Highly related females (relatedness ??0.5) associated more closely than unrelated females. Further, period of the rut as well as male age structure and sex ratio had a significant effect on female association. Our study suggests that the female reindeer association during rut is not only influenced by preference for kin but also by male?Cmale competition and male age as well.