Atmospheric CO2 enrichment alters energy assimilation, investment and allocation in Xanthium strumarium

Energy-use efficiency and energy assimilation, investment and allocation patterns are likely to influence plant growth responses to increasing atmospheric CO2 concentration ([CO2]). Here, we describe the influence of elevated [CO2] on energetic properties as a mechanism of growth responses in Xanthium strumarium. Individuals of X. strumarium were grown at ambient or elevated [CO2] and harvested. Total biomass and energetic construction costs (CC) of leaves, stems, roots and fruits and percentage of total biomass and energy allocated to these components were determined. Photosynthetic energy-use efficiency (PEUE) was calculated as the ratio of total energy gained via photosynthetic activity (Atotal) to leaf CC. Elevated [CO2] increased leaf Atotal, but decreased CC per unit mass of leaves and roots. Consequently, X. strumarium individuals produced more leaf and root biomass at elevated [CO2] without increasing total energy investment in these structures (CCtotal). Whole-plant biomass was associated positively with PEUE. Whole-plant construction required 16.1% less energy than modeled whole-plant energy investment had CC not responded to increased [CO2]. As a physiological mechanism affecting growth, altered energetic properties could positively influence productivity of X. strumarium, and potentially other species, at elevated [CO2].     

Factors influencing the sporulation and cyst formation of Aphanomyces invadans, etiological agent of ulcerative mycosis in Atlantic menhaden, Brevoortia tyrannus

Oomycete infections caused by Aphanomyces invadans occur in freshwater and estuarine fishes around the world. Along the east coast of the USA, skin ulcers caused by A. invadans are prevalent in Atlantic menhaden, Brevoortia tyrannus. From laboratory observations low salinities appear crucial to transmission of the pathogen. To better understand aspects of transmission, we characterized sporulation and cyst formation of secondary zoospores of two isolates of A. invadans at different salinities and temperatures. Sporulation occurred only at low salinities. At room temperature (ca. 20-22 C), using "pond water" augmented with artificial sea salts, the endemic strain WIC and the Thailand strain PA7 of A. invadans produced free-swimming secondary zoospores at salinities of 0, 1 and 2 psu (practical salinity unit = per thousand), but not at 4 psu or higher. Secondary zoospores of another species, ATCC-62427 (Aphanomyces sp.), were observed at 1, 2, 4 and 8 psu but not at 0 and 12 psu. Secondary zoospores of all three isolates, especially WIC, were abundant and motile 1-2 d postsporulation. Sporulation was temperature dependent and occurred over a relatively narrow range. No sporulation occurred at 4, 30 or 35 C for either WIC or PA7. For both strains zoospore production within 1-3 d after the initiation of sporulation was more prolific at 25 C than at 20 and 15 C. At 15 C production of zoospores was sustained over 11 d for WIC and 5 d for PA7. At room temperature single WIC secondary zoospores remained motile 12-18 h. Salinities exceeding 4 psu or vigorous shaking caused immediate cyst formation of WIC secondary zoospores. Exposure to menhaden tissue, but not tissues of other fishes to secondary zoospores (WIC), caused rapid (2 h) cyst formation. Cysts were capable of excysting when transferred to 1 psu water within 2-3 h of cyst formation. Cysts that had remained encysted in 6.5 psu for 24 h did not excyst when transferred to 1 psu water. Salinity and temperature requirements for sporulation indicate that juvenile menhaden must acquire infections during rain or in low salinity oligohaline waters.     

Vitamin D: a hormone for all seasons--how much is enough?

Further understanding of its endocrine mechanisms and increased evidence for autocrine/paracrine actions has recently enhanced our knowledge of the biological activities of the vitamin D metabolite 1,25-dihydroxyvitamin D (1,25(OH)2D). The recognition of the contribution of vitamin D depletion to increased risk of osteoporosis, and most importantly the risk of hip fracture in the elderly, has increased the clinical significance of clinical laboratory testing for vitamin D status. Research has revealed that at least three genes contribute to vitamin D activity within tissues. These are the vitamin D receptor as well as two major vitamin D metabolising enzymes, CYP27B1, responsible for synthesis of 1,25(OH)2D and CYP24, responsible for catabolism of vitamin D metabolites. Current research focuses on the contribution of vitamin D metabolism to increasing vitamin D activity. This is of particular interest in bone forming cells where increased 1,25(OH)2D activity has been proposed to contribute to strengthening the skeleton. As well, solid tumours such as prostate, breast and colon cancers are another increasing area of vitamin D research. The major issues for the clinical laboratory in vitamin D testing include defining clinical decision limits for the interpretation of serum 25-hydroxyvitamin D (25OHD) levels and improving the precision and accuracy of this assay.     

Induction of heme oxygenase-1 inhibits NAD(P)H oxidase activity by down-regulating cytochrome b558 expression via the reduction of heme availability

Heme-oxygenase-1 (HO-1), the rate-limiting enzyme of heme degradation, has powerful anti-oxidant properties related to the production of the reactive oxygen species scavenger bilirubin. However, some data suggest that HO-1 could also inhibit the cellular production of reactive oxygen species. Therefore, we investigated whether the anti-oxidant properties of HO-1 could be mediated by modulation of the activity and/or expression of the heme-containing NAD(P)H oxidase, the main source of the superoxide anion (O(2)(-)) in phagocytic cells. Increasing HO-1 expression in RAW 264.7 macrophages effectively decreased NAD(P)H oxidase activity and expression of gp91(phox), its heme-containing catalytic component, because of deficient protein maturation and increased degradation. Loading cells with heme reversed the decrease in O(2)(-) production and gp91(phox) expression induced by HO-1 overexpression. Similar results were obtained in vivo in rat alveolar macrophages after pharmacological modulation of HO-1 expression or activity. These results show that a decrease in heme content due to HO-1 activation limits heme availability for maturation of the gp91(phox) subunit and assembly of the functional NAD(P)H oxidase. This study provides a new mechanism to explain HO-1 anti-oxidant properties.     

Comparison of cellular response in bovine intervertebral disc cells and articular chondrocytes: effects .of lipopolysaccharide on proteoglycan metabolism

Lipopolysaccharide (LPS) induces matrix degradation and markedly stimulates the production of several cytokines, i.e., interleukin-1β, −6, and −10, by disc cells and chondrocytes. We performed a series of experiments to compare cellular responses of cells from the bovine intervertebral disc (nucleus pulposus and annulus fibrosus) and from bovine articular cartilage to LPS. Alginate beads containing cells isolated from bovine intervertebral discs and articular cartilage were cultured with or without LPS in the presence of 10% fetal bovine serum. The DNA content and the rate of proteoglycan synthesis and degradation were determined. In articular chondrocytes, LPS strongly suppressed cell proliferation and proteoglycan synthesis in a dose-dependent manner and stimulated proteoglycan degradation. Compared with articular chondrocytes, nucleus pulposus cells responded in a similar, although less pronounced manner. However, treatment of annulus fibrosus cells with LPS showed no significant effects on proteoglycan synthesis or degradation. A slight, but statistically significant, inhibition of cell proliferation was observed at high concentrations of LPS in annulus fibrosus cells. Thus, LPS suppressed proteoglycan synthesis and stimulated proteoglycan degradation by articular chondrocytes and nucleus pulposus cells. The effects of LPS on annulus fibrosus cells were minor compared with those on the other two cell types. The dissimilar effects of LPS on the various cell types suggest metabolic differences between these cells and may further indicate a divergence in pathways of LPS signaling and a differential sensitivity to exogenous stimuli such as LPS.This work was supported in part by NIH grants 2-P50-AR39239 and 1-P01-AR48152.     

CCL2 Accelerates Microglia-Mediated Aβ Oligomer Formation and Progression of Neurocognitive Dysfunction

Background

The linkages between neuroinflammation and Alzheimer''s disease (AD) pathogenesis are well established. What is not, however, is how specific immune pathways and proteins affect the disease. To this end, we previously demonstrated that transgenic over-expression of CCL2 enhanced microgliosis and induced diffuse amyloid plaque deposition in Tg2576 mice. This rodent model of AD expresses a Swedish β-amyloid (Aβ) precursor protein mutant.

Methodology/Principal Findings

We now report that CCL2 transgene expression accelerates deficits in spatial and working memory and hippocampal synaptic transmission in β-amyloid precursor protein (APP) mice as early as 2–3 months of age. This is followed by increased numbers of microglia that are seen surrounding Aβ oligomers. CCL2 does not suppress Aβ degradation. Rather, CCL2 and tumor necrosis factor-α directly facilitated Aβ uptake, intracellular Aβ oligomerization, and protein secretion.

Conclusions/Significance

We posit that CCL2 facilitates Aβ oligomer formation in microglia and propose that such events accelerate memory dysfunction by affecting Aβ seeding in the brain.     

A peptidomics study reveals the impressive antimicrobial peptide arsenal of the wax moth Galleria mellonella

The complete antimicrobial peptide repertoire of Galleria mellonella was investigated for the first time by LC/MS. Combining data from separate trypsin, Glu-C and Asp-N digests of immune hemolymph allowed detection of 18 known or putative G. mellonella antimicrobial peptides or proteins, namely lysozyme, moricin-like peptides (5), cecropins (2), gloverin, Gm proline-rich peptide 1, Gm proline-rich peptide 2, Gm anionic peptide 1 (P1-like), Gm anionic peptide 2, galiomicin, gallerimycin, inducible serine protease inhibitor 2, 6tox and heliocin-like peptide. Six of these were previously known only as nucleotide sequences, so this study provides the first evidence for expression of these genes. LC/MS data also provided insight into the expression and processing of the antimicrobial Gm proline-rich peptide 1. The gene for this peptide was isolated and shown to be unique to moths and to have an unusually long precursor region (495 bp). The precursor region contained other proline-rich peptides and LC/MS data suggested that these were being specifically processed and were present in hemolymph at very high levels. This study shows that G. mellonella can concurrently release an impressive array of at least 18 known or putative antimicrobial peptides from 10 families to defend itself against invading microbes.