Decline in self-renewal factors contributes to aging of the stem cell niche in the Drosophila testis

Aging is characterized by compromised organ and tissue function. A decrease in stem cell number and/or activity could lead to the aging-related decline in tissue homeostasis. We have analyzed how the process of aging affects germ line stem cell (GSC) behavior in the Drosophila testis and report that significant changes within the stem cell microenvironment, or niche, occur that contribute to a decline in stem cell number over time. Specifically, somatic niche cells in testes from older males display reduced expression of the cell adhesion molecule DE-cadherin and a key self-renewal signal unpaired (upd). Loss of upd correlates with an overall decrease in stem cells residing within the niche. Conversely, forced expression of upd within niche cells maintains GSCs in older males. Therefore, our data indicate that age-related changes within stem cell niches may be a significant contributing factor to reduced tissue homeostasis and regeneration in older individuals.     

Sampling multiple life stages significantly increases estimates of marine biodiversity

Biodiversity assessments are critical for setting conservation priorities, understanding ecosystem function and establishing a baseline to monitor change. Surveys of marine biodiversity that rely almost entirely on sampling adult organisms underestimate diversity because they tend to be limited to habitat types and individuals that can be easily surveyed. Many marine animals have planktonic larvae that can be sampled from the water column at shallow depths. This life stage often is overlooked in surveys but can be used to relatively rapidly document diversity, especially for the many species that are rare or live cryptically as adults. Using DNA barcode data from samples of nemertean worms collected in three biogeographical regions—Northeastern Pacific, the Caribbean Sea and Eastern Tropical Pacific—we found that most species were collected as either benthic adults or planktonic larvae but seldom in both stages. Randomization tests show that this deficit of operational taxonomic units collected as both adults and larvae is extremely unlikely if larvae and adults were drawn from the same pool of species. This effect persists even in well-studied faunas. These results suggest that sampling planktonic larvae offers access to a different subset of species and thus significantly increases estimates of biodiversity compared to sampling adults alone. Spanish abstract is available in the electronic supplementary material.     

Expression and regulation of inducible IkappaB kinase (IKK-i) in human fibroblast-like synoviocytes

IkappaB kinase (IKK) plays a key role in the regulation of nuclear factor kappaB (NF-kappaB). We previously demonstrated the expression of two kinases, IKK1 and IKK2, in fibroblast-like synoviocytes (FLS) and determined their functional consequences for inflammatory gene expression in vitro and in vivo. Recently, a novel inducible IkappaB kinase has been described, namely, IKK-i or IKK-epsilon, which is functionally and structurally distinct from constitutively expressed IKK1 and IKK2. Therefore, we investigated the expression and regulation of this novel kinase in FLS from patients with rheumatoid arthritis and osteoarthritis. Interestingly, constitutive gene expression and protein expression were observed in all cell lines examined. TNFalpha stimulation for 24 h increased IKK-i expression 7.2 +/- 1.8-fold in FLS (P < 0.02). IL-1 also significantly increased IKK-i gene expression. Time course experiments demonstrated that IKK-i gene expression increased within 3 h of TNFalpha stimulation and persisted for at least 24 h. Dose-response studies showed that as little as 1 ng/ml of TNFalpha increased IKK-i gene expression. Constitutive IKK-1 gene expression was also noted in rheumatoid arthritis, osteoarthritis, and normal synovium. This is the first report demonstrating constitutive expression and cytokine regulation of this novel kinase in primary human synovial cells.     

NF-kappa B regulation by I kappa B kinase-2 in rheumatoid arthritis synoviocytes

IkappaB kinase-1 and IkappaB kinase-2 (IKK1 and IKK2; also called IKKalpha and IKKbeta, respectively) are part of the signal complex that regulates NF-kappaB activity in many cell types, including fibroblast-like synoviocytes (FLS). We determined which of these two kinases is responsible for cytokine-induced NF-kappaB activation in synoviocytes and assessed the functional consequences of IKK1 or IKK2 overexpression and inhibition. FLS were infected with adenovirus constructs encoding either wild-type (wt) IKK1 or IKK2, the dominant negative (dn) mutant of both kinases, or a control construct encoding green fluorescence protein. Analysis of the NF-kappaB pathway revealed that cytokine-induced IKK activation, IkappaB degradation, and NF-kappaB activation was prevented in cells expressing the IKK2 dn mutant, whereas baseline NF-kappaB activity was increased by IKK2 wt. In addition, synthesis of IL-6 and IL-8, as well as expression of ICAM-1 and collagenase, was only increased by IKK2 wt, and their cytokine-induced production was abrogated by IKK2 dn mutant. However, the IKK1 dn mutant did not inhibit cytokine-mediated activation of NF-kappaB or any of the functional assays. These data indicate that IKK2 is the key convergence pathway for cytokine-induced NF-kappaB activation. Furthermore, IKK2 regulates adhesion molecule, matrix metalloproteinase, and cytokine production in FLS.     

A novel autocrine pathway of tumor escape from immune recognition: melanoma cell lines produce a soluble protein that diminishes expression of the gene encoding the melanocyte lineage melan-A/MART-1 antigen through down-modulation of its promoter

We have observed that malignant melanoma cells produce a soluble protein factor(s), which down-regulates melanocyte lineage Melan-A/MART-1 Ag expression by melanoma cells with concomitant loss of recognition by Melan-A/MART-1-specific T cells. This down-modulation of Melan-A/MART-1 expression, which we refer to as "Ag silencing," is mediated via its minimal promoter, whereas the promoter for the restricting Ag-presenting HLA-A2 molecule is not affected. Significantly, this Ag silencing is reversible, as removal of factor-containing supernatants from Melan-A/MART-1-expressing cells results in up-regulation of the promoter for the gene encoding this Ag, and renewed expression of the protein. We have evaluated over 20 known factors, none of which accounts for the Ag-silencing activity of the melanoma cell culture supernatants. The existence of this autocrine pathway provides an additional novel explanation for melanoma tumor progression in vivo in the presence of CTL specific for this melanocyte lineage Ag. These observations may have important implications for Melan-A/MART-1-specific CTL-mediated immunotherapy of melanoma tumors.     

The formation of migratory ripples in a mixed species bacterial biofilm growing in turbulent flow

Mixed-species biofilms, consisting of Klebsiella pneumoniae , Pseudomonas aeruginosa , Pseudomonas fluorescens and Stenotrophomonas maltophilia , were grown in glass flow cells under either laminar or turbulent flow. The biofilms grown in laminar flow consisted of roughly circular-shaped microcolonies separated by water channels. In contrast, biofilm microcolonies grown in turbulent flow were elongated in the downstream direction, forming filamentous 'streamers'. Moreover, biofilms growing in turbulent flow developed extensive patches of ripple-like structures between 9 and 13 days of growth. Using time-lapse microscopic imaging, we discovered that the biofilm ripples migrated downstream. The morphology and the migration velocity of the ripples varied with short-term changes in the bulk liquid flow velocity. The ripples had a maximum migration velocity of 800 μm h⁻¹ (2.2 × 10⁻⁷ m s⁻¹) when the liquid flow velocity was 0.5 m s⁻¹ (Reynolds number = 1800). This work challenges the commonly held assumption that biofilm structures remain at the same location on a surface until they eventually detach.     

The investigation of cytosolic phospholipase A2 using ELISA

Two studies of the behaviour of cytosolic phospholipase A(2) (cPLA(2)) in the red blood cell (RBC), as measured by ELISA, are described. In the first study we show a significant increase in cPLA(2) in patients with schizophrenia compared to controls and suggest that this measure, if corroborated, could be used as a diagnostic marker. In a second study we found that washing the RBC introduced an unknown confounding variable which led us to reject this study. A subsequent investigation of washing red cells showed that the washing effect may be due to a plasma factor likely to be more than 5kDa MW which can be removed from red cells by washing with buffers. When the cells are washed, the concentration of cPLA(2) in the red cell, as measured by ELISA, significantly increases. We advise against washing the red cell in any study that involves measuring cPLA(2) by ELISA.     

Influence of roots and climate on mineral and trace element storage and flux in tropical mangrove soils

The storage and flux of various mineral and trace elements in soils (0–30cm depth) were examined in relation to monsoonal rains and fine root biomass in four mangrove forests of different age and type in southern Thailand. The onset of the wet SW monsoon resulted in the percolation and dilution of porewater solutes by rainwater and by less saline tidal water, as indicated by shifts in Eh, pH and porewater SO₄/Cl ratios. This is contrary to temperate intertidal environments where seasonal patterns of porewater constituents, and biological and biogeochemical activities, are strongly cued to temperature. Fluxes across the soil–water interface were most often not statistically significant. Concentration of dissolved porewater metals were dominated by Fe, Mn, Al, Mo and Zn. The decreasing order of solid-phase element inventories in these soils, on average, was: Al, S, Fe, Na, Mg, K, Ca, N, P, Mn, V, Zn, Cr, Ni, As, Co, Cu, Pb, Mo, Cd and Hg. There were no gradients in concentrations of dissolved or solid-phase elements with increasing soil depth. This phenomenon was attributed to physical and biological processes, including the presence and activities of roots and tidal recharge of soil water. Fine dead roots were storage sites for most mineral and trace elements, as some elements in roots composed a significant fraction (5%) of the total soil pool. Analysis of S and Fe concentration differences between live and dead roots suggested extensive formation of pyrite associated with dead roots; correlation analysis suggested that trace metals coprecipitated with pyrite. An analysis of inventories and release/uptake rates indicate turnover of the N, P, Na and Ca soil pools equivalent to other tropical forests; turnover was slow (decades to centuries) for S, Fe, K and trace elements. Our results indicate that mineral and trace element cycling in these soils are characterized by net storage, with net accumulation of most elements much greater than uptake and release by tree roots.     

Pain and compassion in the neonatal unit -- a neonatologist's view

Research has shown that even extremely premature babies are sufficiently developed, anatomically and physiologically, to be capable of experiencing and responding to pain. All newborn infants and especially those who require intensive care in the first days of life are exposed to some painful procedures. Part of the neonatologist's role is the detection and management of pain in these infants. Difficult challenges come with this role. All medications carry known or potential adverse effects and limited research has been done in this vulnerable population. The benefits and risks of all available pain-relieving measures should be balanced when planning management. Compassion is no excuse for a high incidence of undesirable or dangerous side effects. We must proceed with great care.