Microtubule dynamics in a cytosolic extract of fetal rat brain

Brain microtubule dynamics were studied by video-enhanced differential interference contrast microscopy in a cytosolic extract from fetal rat brain, prepared under conditions designed to produce minimal alterations in microtubule stability. With urchin sperm axoneme fragments as nucleation seeds, the extract was shown to support cellular-like microtubule dynamics. Microtubules elongated from one end of the axonemes, and did not spontaneously self-assemble in the absence of axonemes. The following microtubule kinetic parameters were measured in the extract: velocity of elongation (8.1 mm/min), velocity of rapid shortening (5.8 mm/min), catastrophe frequency (0.17 min-1), and rescue frequency (1 min-1). These parameters were in close agreement with reported values for growth cones of living neurons. Microtubule properties in the fetal brain extract were shown to be affected by agents with known effects on the cytoskeleton. pp60c-src, a tyrosine kinase important in cell adhesion molecule-dependent axon growth, caused small increases in the frequency of microtubule catastrophe (0.31 min-1) and rescue (2 min-1) without changing the velocities of elongation or rapid-shortening. Although pp60c-src phosphorylated purified porcine brain tubulin in vitro, it did not elicit significant changes in its polymerization properties, suggesting that other cytoskeletal proteins in the brain extract are involved in modulating microtubule dynamics. The cytosolic extract of fetal rat brain provides a useful system for studying regulation of microtubule assembly in neuronal growth cones.     

Airway cellularity, lipid laden macrophages and microbiology of gastric juice and airways in children with reflux oesophagitis

Background and methods

Human metapneumovirus (hMPV) is a recently discovered respiratory virus associated with bronchiolitis, pneumonia, croup and exacerbations of asthma. Since respiratory viruses are frequently detected in patients with acute exacerbations of COPD (AE-COPD) it was our aim to investigate the frequency of hMPV detection in a prospective cohort of hospitalized patients with AE-COPD compared to patients with stable COPD and to smokers without by means of quantitative real-time RT-PCR.

Results

We analysed nasal lavage and induced sputum of 130 patients with AE-COPD, 65 patients with stable COPD and 34 smokers without COPD. HMPV was detected in 3/130 (2.3%) AE-COPD patients with a mean of 6.5 × 10⁵ viral copies/ml in nasal lavage and 1.88 × 10⁵ viral copies/ml in induced sputum. It was not found in patients with stable COPD or smokers without COPD.

Conclusion

HMPV is only found in a very small number of patients with AE-COPD. However it should be considered as a further possible viral trigger of AE-COPD because asymptomatic carriage is unlikely.     

Low Omega-3 Index in Pregnancy Is a Possible Biological Risk Factor for Postpartum Depression

Background

Depression is a common disorder affecting 10–15% women in the postpartum period. Postpartum depression can disrupt early mother-infant interaction, and constitutes a risk factor for early child development. Recently, attention has been drawn to the hypothesis that a low intake of seafood in pregnancy can be a risk factor for postpartum depression. Seafood is a unique dietary source of the marine omega-3 fatty acids and is a natural part of a healthy balanced diet that is especially important during pregnancy.

Methods

In a community based prospective cohort in a municipality in Western Norway, we investigated both nutritional and psychological risk factors for postpartum depression. The source population was all women who were pregnant within the period November 2009 - June 2011. The fatty acid status in red blood cells was assessed in the 28^th gestation week and participants were screened for postpartum depression using the Edinburgh Postnatal Depression Scale (EPDS) three months after delivery. The aim of the present study was to investigate if a low omega-3 index in pregnancy is a possible risk factor for postpartum depression.

Results

In a simple regression model, the omega-3 index was associated with the EPDS score in a nonlinear inverse manner with an R square of 19. Thus, the low omega-3 index explained 19% of the variance in the EPDS score. The DPA content, DHA content, omega-3 index, omega-3/omega-6 ratio, total HUFA score, and the omega-3 HUFA score were all inversely correlated with the EPDS score. The EPDS scores of participants in the lowest omega-3 index quartile were significantly different to the three other omega-3 index quartiles.

Conclusion

In this study population, a low omega-3 index in late pregnancy was associated with higher depression score three months postpartum.     

Anaerobic degradation of papermill sludge in a two-phase digester containing rumen microorganisms and colonized polyurethane foam

Summary The use of reticulated polyurethane foam as a support material for the immobilization of methanogenic associations and its application to the anaerobic treatment of fine particulate solid wastes was investigated. The colonization of polyurethane support particles in a continuous upflow reactor fed on a mixture of acetate, propionate and butyrate, was both rapid and dense. The combination of rumen microorganisms and colonized support particles in a two-phase digester resulted in an efficient anaerobic decomposition of papermill sludge.     

Annulus cells release ATP in response to vibratory loading in vitro

Mechanical forces regulate the developmental path and phenotype of a variety of tissues and cultured cells. Vibratory loading as a mechanical stimulus occurs in connective tissues due to energy returned from ground reaction forces, as well as a mechanical input from use of motorized tools and vehicles. Structures in the spine may be particularly at risk when exposed to destructive vibratory stimuli. Cells from many tissues respond to mechanical stimuli, such as fluid flow, by increasing intracellular calcium concentration ([Ca(2+)](ic)) and releasing adenosine 5'-triphosphate (ATP), extracellularly, as a mediator to activate signaling pathways. Therefore, we examined whether ATP is released from rabbit (rAN) and human (hAN) intervertebral disc annulus cells in response to vibratory loading. ATP release from annulus cells by vibratory stimulation as well as in control cells was quantitated using a firefly luciferin-luciferase assay. Cultured hAN and rAN cells had a basal level of extracellular ATP ([ATP](ec)) in the range of 1-1.5 nM. Vibratory loading of hAN cells stimulated ATP release, reaching a net maximum [ATP] within 10 min of continuous vibration, and shortly thereafter, [ATP] declined and returned to below baseline level. [ATP] in the supernatant fluid of hAN cells was significantly reduced compared to the control level when the cells received vibration for longer than 15 min. In rAN cells, [ATP] was increased in response to vibratory loading, attaining a level significantly greater than that of the control after 30 min of continuous vibration. Results of the current study show that resting annulus cells secrete ATP and maintain a basal [ATP](ec). Annulus cells may use this nucleotide as a signaling messenger in an autocrine/paracrine fashion in response to vibratory loading. Rapid degradation of ATP to ADP may alternatively modulate cellular responses. It is hypothesized that exposure to repetitive, complex vibration regimens may activate signaling pathways that regulate matrix destruction in the disc. As in tendon cells, ATP may block subsequent responses to load and modulate the vibration response. Rabbit annulus cells were used as a readily obtainable source of cells in development of an animal model for testing effects of vibration on the disc. Human cells obtained from discarded surgical specimens were used to correlate responses of animal to human cells.     

Oxido-reduction is not the only mechanism allowing ions to traverse the ferritin protein shell

Background

Most models for ferritin iron release are based on reduction and chelation of iron. However, newer models showing direct Fe(III) chelation from ferritin have been proposed. Fe(III) chelation reactions are facilitated by gated pores that regulate the opening and closing of the channels.

Scope of review

Results suggest that iron core reduction releases hydroxide and phosphate ions that exit the ferritin interior to compensate for the negative charge of the incoming electrons. Additionally, chloride ions are pumped into ferritin during the reduction process as part of a charge balance reaction. The mechanism of anion import or export is not known but is a natural process because phosphate is a native component of the iron mineral core and non-native anions have been incorporated into ferritin in vitro. Anion transfer across the ferritin protein shell conflicts with spin probe studies showing that anions are not easily incorporated into ferritin. To accommodate both of these observations, ferritin must possess a mechanism that selects specific anions for transport into or out of ferritin. Recently, a gated pore mechanism to open the 3-fold channels was proposed and might explain how anions and chelators can penetrate the protein shell for binding or for direct chelation of iron.

Conclusions and general significance

These proposed mechanisms are used to evaluate three in vivo iron release models based on (1) equilibrium between ferritin iron and cytosolic iron, (2) iron release by degradation of ferritin in the lysosome, and (3) metallo-chaperone mediated iron release from ferritin.     

Tripeptidyl peptidase II promotes fat formation in a conserved fashion

Tripeptidyl peptidase II (TPPII) is a multifunctional and evolutionarily conserved protease. In the mammalian hypothalamus, TPPII has a proposed anti-satiety role affected by degradation of the satiety hormone cholecystokinin 8. Here, we show that TPPII also regulates the metabolic homoeostasis of Caenorhabditis elegans; TPPII RNA interference (RNAi) decreases worm fat stores. However, this occurs independently of feeding behaviour and seems to be a function within fat-storing tissues. In mammalian cell culture, TPPII stimulates adipogenesis and TPPII RNAi blocks adipogenesis. The pro-adipogenic action of TPPII seems to be independent of protease function, as catalytically inactive TPPII also increases adipogenesis. Mice that were homozygous for an insertion in the Tpp2 locus were embryonic lethal. However, Tpp2 heterozygous mutants were lean compared with wild-type littermates, although food intake was normal. These findings indicate that TPPII has central and peripheral roles in regulating metabolism and that TPPII actions in fat-storing tissues might be an ancient function carried out in a protease-independent manner.