Base cation biogeochemistry and weathering under oak and pine: a controlled long-term experiment

Large earthen-walled lysimeters at the San Dimas Experimental Forest in southern California present a unique opportunity to assess vegetation effects on biogeochemical processes and cation release by weathering in controlled soil-vegetation systems where archived samples of soil parent material are available for comparison. The lysimeters were filled in 1937 with homogenized fine sandy loam derived on site from the weathering of diorite, and planted in 1946 with scrub oak (Quercus dumosa) and Coulter pine (Pinus coulteri). Changes in base cation contents were measured in above-ground biomass, and total and exchangeable soil pools to a depth of 1 meter. All cations in the non-exchangeable soil pool decreased relative to the initial fill material, indicating release by weathering. Sodium and K were depleted from both exchangeable and non-exchangeable pools of the soils. Plant uptake of Na was minimal, whereas K storage in vegetation exceeded the loss from the exchangeable soil pool. In both soil-vegetation systems, but especially for oak, there was an increase in exchangeable Ca and Mg. For all base cations, storage in above-ground biomass was greater for oak, whereas losses by weathering from the non-exchangeable soil pool were greater under pine. Strong evidence supports biocycling as a controlling mechanism resulting in greater Ca and Mg release by weathering under pine. In addition, decreases in non-exchangeable Ca and Mg were strongly correlated to decrease in Si under oak, whereas no correlation was observed under pine. We conclude that weathering reactions or stoichiometry differed between vegetation types.Corresponding author     

Differential tissue distribution, developmental programming, estrogen regulation and promoter characteristics of cyp19 genes in teleost fish

Teleost fish are characterized by exceptionally high levels of brain estrogen biosynthesis when compared to the brains of other vertebrates or to the ovaries of the same fish. Goldfish (Carassius auratus) and zebrafish (Danio rerio) have utility as complementary models for understanding the molecular basis and functional significance of exaggerated neural estrogen biosynthesis. Multiple cytochrome P450 aromatase (P450arom) cDNAs that derive from separate gene loci (cyp19a and cyp19b) are differentially expressed in brain (P450aromBA) and ovary (P450aromAB) and have a different developmental program (BA) and response to estrogen upregulation (B only). As measured by increased P450aromB mRNA, a functional estrogen response system is first detected 24–48 h post-fertilization (hpf), consistent with the onset of estrogen receptor (ER) expression (, β, and γ). The 5′-flanking region of the cyp19b gene has a TATA box, two estrogen response elements (EREs), an ERE half-site (ERE1/2), a nerve growth factor inducible-B protein (NGFI-B)/Nur77 responsive element (NBRE) binding site, and a sequence identical to the zebrafish GATA-2 gene neural specific enhancer. The cyp19a promoter region has TATA and CAAT boxes, a steroidogenic factor-1 (SF-1) binding site, and two aryl hydrocarbon receptor (AhR)/AhR nuclear translocator factor (ARNT) binding motifs. Both genes have multiple potential SRY/SOX binding sites (16 and 8 in cyp19b and cyp19a, respectively). Luciferase reporters have basal promoter activity in GH3 cells, but differences (ab) are opposite to fish pituitary (ba). When microinjected into fertilized zebrafish eggs, a cyp19b promoter-driven green fluorescent protein (GFP) reporter (but not cyp19a) is expressed in neurons of 30–48 hpf embryos, most prominently in retinal ganglion cells (RGCs) and their projections to optic tectum. Further studies are required to identify functionally relevant cis-elements and cellular factors, and to determine the regulatory role of estrogen in neurodevelopment.     

The glycosylation of human myelin basic protein at threonines 95 and 98 occurs sequentially

Human myelin basic protein (MBP) was glycosylated by the enzyme, UDP-GalNAc:polypeptide N-acetylgalactosaminyl transferase (EC 2.4.2.41). A maximum of 1.7 mol of GalNAc was transferred to basic protein on threonines 95 and 98 of the protein. Proton NMR studies of basic protein glycosylated with 0.48-1.7 mol of GalNAc/mol of MBP showed that the order of addition to the two threonine residues is not random but sequential. The Thr-95 resonances shifted downfield, followed by the downfield shift of the Thr-98 resonances with increasing glycosylation. Since this peptide segment of the molecule is highly structured, conformational factors are probably responsible for this directed addition.     

Treatment of canine aspiration pneumonitis: fluid volume reduction vs. fluid volume expansion

The aspiration of gastric acid causes pulmonary edema and hypoxemia. One approach to the management of this syndrome is to raise cardiac output (Qt) and O2 delivery (QO2) to ensure tissue oxygenation (VO2) at the risk of increasing the edema. Another approach reduces the edema by reducing pulmonary microvascular pressure (Pmv) at the risk of reducing QO2 and VO2. We compared these approaches in 24 anesthetized, ventilated dogs with pulmonary wedge pressure (Ppw), a clinical approximation of Pmv, of 12.5 mmHg. Before and again 1 h after endobronchial instillation of 0.1 N HCl, we measured Qt, QO2, VO2, venous admixture, and in vivo extravascular lung liquid. The dogs were then randomly divided into four equal groups: 1) 12.5 mmHg Ppw, high Qt; 2) 7.5 mmHg Ppw, intermediate Qt; 3) 4.5 mmHg Ppw, low Qt; and 4) 4.5 mmHg Ppw plus dopamine, intermediate Qt. Measured values were followed for 4 more h, after which the lungs were excised to compare wet weight-to-body weight ratios (W/B). When plasmapheresis reduced Ppw at 1 h, edema did not increase further and W/B of groups 2 (21 +/- 3), 3 (18 +/- 3), and 4 (22 +/- 3) were significantly less than in group 1 (27 +/- 3) (P less than 0.001). Although Qt decreased with Ppw, increased hematocrit and reduced venous admixture maintained QO2 in group 2 but not in group 3. In group 4 an intermediate Qt maintained QO2 even at 4.5 mmHg Ppw but edema increased to the group 2 level presumably because Pmv rose with Qt on dopamine. VO2 remained constant over time in each group. These data demonstrate that canine HCl-induced pulmonary edema, measured in vivo or gravimetrically, is very sensitive to reductions in Pmv. Moreover, the lowest Pmv (and QO2) was well tolerated because an O2 supply dependency of VO2 was not observed.     

Long-term interleukin-6 levels and subsequent risk of coronary heart disease: two new prospective studies and a systematic review

Background

The relevance to coronary heart disease (CHD) of cytokines that govern inflammatory cascades, such as interleukin-6 (IL-6), may be underestimated because such mediators are short acting and prone to fluctuations. We evaluated associations of long-term circulating IL-6 levels with CHD risk (defined as nonfatal myocardial infarction [MI] or fatal CHD) in two population-based cohorts, involving serial measurements to enable correction for within-person variability. We updated a systematic review to put the new findings in context.

Methods and Findings

Measurements were made in samples obtained at baseline from 2,138 patients who had a first-ever nonfatal MI or died of CHD during follow-up, and from 4,267 controls in two cohorts comprising 24,230 participants. Correction for within-person variability was made using data from repeat measurements taken several years apart in several hundred participants. The year-to-year variability of IL-6 values within individuals was relatively high (regression dilution ratios of 0.41, 95% confidence interval [CI] 0.28–0.53, over 4 y, and 0.35, 95% CI 0.23–0.48, over 12 y). Ignoring this variability, we found an odds ratio for CHD, adjusted for several established risk factors, of 1.46 (95% CI 1.29–1.65) per 2 standard deviation (SD) increase of baseline IL-6 values, similar to that for baseline C-reactive protein. After correction for within-person variability, the odds ratio for CHD was 2.14 (95% CI 1.45–3.15) with long-term average (“usual”) IL-6, similar to those for some established risk factors. Increasing IL-6 levels were associated with progressively increasing CHD risk. An updated systematic review of electronic databases and other sources identified 15 relevant previous population-based prospective studies of IL-6 and clinical coronary outcomes (i.e., MI or coronary death). Including the two current studies, the 17 available prospective studies gave a combined odds ratio of 1.61 (95% CI 1.42–1.83) per 2 SD increase in baseline IL-6 (corresponding to an odds ratio of 3.34 [95% CI 2.45–4.56] per 2 SD increase in usual [long-term average] IL-6 levels).

Conclusions

Long-term IL-6 levels are associated with CHD risk about as strongly as are some major established risk factors, but causality remains uncertain. These findings highlight the potential relevance of IL-6–mediated pathways to CHD.     

Protein engineering of toluene ortho-monooxygenase of Burkholderia cepacia G4 for regiospecific hydroxylation of indole to form various indigoid compounds

Previous work showed that random mutagenesis produced a mutant of toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 containing the V106A substitution in the hydroxylase -subunit (TomA3) that changed the color of the cell suspension from wild-type brown to green in rich medium. Here, DNA shuffling was used to isolate a random TOM mutant that turned blue due to mutation TomA3 A113V. To better understand the TOM reaction mechanism, we studied the specificity of indole hydroxylation using a spectrum of colored TOM mutants expressed in Escherichia coli TG1 and formed as a result of saturation mutagenesis at TomA3 positions A113 and V106. Colonies expressing these altered enzymes ranged in color from blue through green and purple to orange; and the enzyme products were identified using thin-layer chromatography, high performance liquid chromatography, and liquid chromatography–mass spectroscopy. Derived from the single TOM template, enzymes were identified that produced primarily isoindigo (wild-type TOM), indigo (A113V), indirubin (A113I), and isatin (A113H and V106A/A113G). The discovery that wild-type TOM formed isoindigo via C-2 hydroxylation of the indole pyrrole ring makes this the first oxygenase shown to form this compound. Variant TOM A113G was unable to form indigo, indirubin, or isoindigo (did not hydroxylate the indole pyrrole ring), but produced 4-hydroxyindole and unknown yellow compounds from C-4 hydroxylation of the indole benzene ring. Mutations at V106 in addition to A113G restored C-3 indole oxidation, so along with C-2 indole oxidation, isatin, indigo, and indirubin were formed. Other TomA3 V106/A113 mutants with hydrophobic, polar, or charged amino acids in place of the Val and/or Ala residues hydroxylated indole at the C-3 and C-2 positions, forming isatin, indigo, and indirubin in a variety of distributions. Hence, for the first time, a single enzyme was genetically modified to produce a wide range of colors from indole.     

Molecular Biophysics of Orai Store-Operated Ca2+ Channels

Upon endoplasmic reticulum Ca²⁺ store depletion, Orai channels in the plasma membrane are activated directly by endoplasmic reticulum-resident STIM proteins to generate the Ca²⁺-selective, Ca²⁺ release-activated Ca²⁺ (CRAC) current. After the molecular identification of Orai, a plethora of functional and biochemical studies sought to compare Orai homologs, determine their stoichiometry, identify structural domains responsible for the biophysical fingerprint of the CRAC current, identify the physiological functions, and investigate Orai homologs as potential therapeutic targets. Subsequently, the solved crystal structure of Drosophila Orai (dOrai) substantiated many findings from structure-function studies, but also revealed an unexpected hexameric structure. In this review, we explore Orai channels as elucidated by functional and biochemical studies, analyze the dOrai crystal structure and its implications for Orai channel function, and present newly available information from molecular dynamics simulations that shed light on Orai channel gating and permeation.     

Social organization in a flatworm: trematode parasites form soldier and reproductive castes

In some of the most complex animal societies, individuals exhibit a cooperative division of labour to form castes. The most pronounced types of caste formation involve reproductive and non-reproductive forms that are morphologically distinct. In colonies comprising separate or mobile individuals, this type of caste formation has been recognized only among the arthropods, sea anemones and mole-rats. Here, we document physical and behavioural caste formation in a flatworm. Trematode flatworm parasites undergo repeated clonal reproduction of ‘parthenitae’ within their molluscan hosts forming colonies. We present experimental and observational data demonstrating specialization among trematode parthenitae to form distinct soldier and reproductive castes. Soldiers do not reproduce, have relatively large mouthparts, and are much smaller and thinner than reproductives. Soldiers are also more active, and are disproportionally common in areas of the host where invasions occur. Further, only soldiers readily and consistently attack heterospecifics and conspecifics from other colonies. The division of labour described here for trematodes is strongly analogous to that characterizing other social systems with a soldier caste. The parallel caste formation in these systems, despite varying reproductive mode and taxonomic affiliation, indicates the general importance of ecological factors in influencing the evolution of social behaviour. Further, the ‘recognition of self’ and the defence of the infected host body from invading parasites are comparable to aspects of immune defence. A division of labour is probably widespread among trematodes and trematode species encompass considerable taxonomic, life history and environmental diversity. Trematodes should therefore provide new, fruitful systems to investigate the ecology and evolution of sociality.     

Effects of temperature on respiration and acid-base balance in a monitor lizard

Summary Ventilation, gas exchange, blood gas tensions and arterial pH were measured simultaneously in monitor lizards,Varanus exanthematicus. In contrast to previously studied poikilotherms, the arterial pH is independent of body temperature within the normally encountered temperature range (Fig. 1). This exception to the relative alkalinity concept (Rahn, 1966) is correlated with the finding thatV. exanthematicus maintains a constant ratio of ventilation to oxygen uptake (and CO₂ production) at different temperatures (Fig. 3). The increase in arterial (Fig. 1) is related to an increase in physiological dead space; i.e., alveolar ventilation increases less with temperature than total ventilation (Fig. 4). This may result from the increased frequency of breathing which results in a reduced breath holding time (Fig. 2). Varanid lizards have a higher oxygen requirement than other reptiles. This is reflected in the control of ventilation, the specialized lung morphology, the high arterial saturation due to low intracardiac shunting, pH regulation and other mammal-like features ofVaranus.