Which method of estimating renal function is the best predictor of mortality after coronary artery bypass grafting?

Objectives

Definitions of renal function in patients undergoing coronary artery bypass graft surgery (CABG) vary in the literature. We sought to investigate which method of estimating renal function is the best predictor of mortality after CABG.

Methods

We analysed the preoperative and postoperative renal function data from all patients undergoing isolated CABG from January 1998 through December 2007. Preoperative and postoperative renal function was estimated using serum creatinine (SeCr) levels, creatinine clearance (CrCl) determined by the Cockcroft-Gault formula and the glomerular filtration rate (e-GFR) estimated by the Modification of Diet in Renal Disease (MDRD) formula. Receiver operator characteristic (ROC) curves and area under the ROC curves were calculated.

Results

In 9987 patients, CrCl had the best discriminatory power to predict early as well as late mortality, followed by e-GFR and finally SeCr. The odds ratios for preoperative parameters for early mortality were closer to 1 than those of the postoperative parameters.

Conclusions

Renal function determined by the Cockcroft-Gault formula is the best predictor of early and late mortality after CABG. The relationship between renal function and mortality is non-linear. Renal function as a variable in risk scoring systems such as the EuroSCORE needs to be reconsidered.     

How useful is the mutualism-parasitism continuum of arbuscular mycorrhizal functioning?

Background

A recent review in this journal puts forward the premise that our recent studies have resulted in our questioning the validity of the so-called mutualism-parasitism continuum of functioning of arbuscular mycorrhizas. This premise is incorrect and appears largely to result from a misunderstanding of terminology.

Scope and conclusions

We clarify a comment in one of our publications that influenced the previous review, which contains several statements that do not accurately represent our views. Our research has overturned not the continuum concept itself, but some past ideas about the balance of resources traded between AM fungi and plants. Of course, we recognize that outcomes of AM symbiosis in relation to the non-mycorrhizal (NM) state are strongly influenced by many environmental factors. Nevertheless, underlying resource trade is always a key determinant of costs and benefits of the symbiosis for both partners. In this context, we address uncertainties and contradictory ideas about mechanisms, causes, effects and outcomes in AM symbioses that occur in the literature, and issues of relevance of research at different scales. We also discuss semantics that can cause confusion. Finally, we assess how useful the mutualism-parasitism continuum is for design of hypothesis-driven experiments to disentangle the complex interactions that determine growth of AM plants, i.e. the so-called emergent properties.     

Which is the phyte in epiphyte?

The term “Epiphyte” has been used for a plant growing on any object, and also for any organism growing on a plant. Evidence from analogy, dictionaries, use and precedence supports the two interpretations equally. We recommend that “epiphyte” be used only for an organism growing on a plant.     

Two theories of origin of the land-plant sporophyte: Which is left standing?

Questions concerning the two competing theories of the development of alternating generations in land plants, the homologous theory and the antithetic theory, have never been fully resolved. In the majority of recent accounts there appears to have been increasing de facto support (if one considers the ontogenetic processes and phylogenetic consequences discussed) for the antithetic theory. However, this preference is usually not plainly stated (as such) in these discussions, and some support has also continued for the homologous theory. The crux of both theories (homologous and antithetic) centers upon how the sporophyte may have originated in the life cycle. One problem with the homologous theory is that it is not made explicit how the development of a dependent sporophyte could have occurred in the life cycle (when the precedent organisms are considered to have had free-living, putatively similar, gametophytes and sporophytes). The antithetic theory, by contrast, offers a definite ontogenetic mechanism or process (retention of the zygote on the gametophyte, delay of zygotic meiosis, with zygotic mitoses occurring first) by which a dependent sporophyte might have originated and persisted, in the context of a life cycle formerly lacking a sporophyte generation. Also, a review of a variety of evidence (morphological, cytological, biochemical, etc.) would appear to lend more support to the antithetic theory than to the homologous theory. In discussing types of algae now known to be most clearly related to land plants (i.e., charophytes, particularly advanced forms), the type of life cycle exhibited by these particular algae (haplontic, with zygotic meiosis; no sporophyte present) suggests that only an antithetic origin of the sporophyte in land plants is actually feasible.     

Which is the correct scientific name,Tutcheria championii or T. spectabilis?

In accordance with the International Code of Botanical Nomenclature, the name Tutcheria spectabilis Dunn (1908) has priority over the later name Tutcheria championii Nakai (1940) which is illegitimate, despite the fact that the latter name has been used in some recent Chinese floras.     

How stable is stable? Function versus community composition.

The microbial community dynamics of a functionally stable, well-mixed, methanogenic reactor fed with glucose were analyzed over a 605-day period. The reactor maintained constant pH and chemical oxygen demand removal during this period. Thirty-six rrn clones from each of seven sampling events were analyzed by amplified ribosomal DNA restriction analysis (ARDRA) for the Bacteria and Archaea domains and by sequence analysis of dominant members of the community. Operational taxonomic units (OTUs), distinguished as unique ARDRA patterns, showed reproducible distribution for three sample replicates. The highest diversity was observed in the Bacteria domain. The 16S ribosomal DNA Bacteria clone library contained 75 OTUs, with the dominant OTU accounting for 13% of the total clones, but just 21 Archaea OTUs were found, and the most prominent OTU represented 50% of the clones from the respective library. Succession in methanogenic populations was observed, and two periods were distinguished: in the first, Methanobacterium formicicum was dominant, and in the second, Methanosarcina mazei and a Methanobacterium bryantii-related organism were dominant. Higher variability in Bacteria populations was detected, and the temporal OTU distribution suggested a chaotic pattern. Although dominant OTUs were constantly replaced from one sampling point to the next, phylogenetic analysis indicated that inferred physiologic changes in the community were not as dramatic as were genetic changes. Seven of eight dominant OTUs during the first period clustered with the spirochete group, although a cyclic pattern of substitution occurred among members within this order. A more flexible community structure characterized the second period, since a sequential replacement of a Eubacterium-related organism by an unrelated deep-branched organism and finally by a Propionibacterium-like species was observed. Metabolic differences among the dominant fermenters detected suggest that changes in carbon and electron flow occurred during the stable performance and indicate that an extremely dynamic community can maintain a stable ecosystem function.     

Which stage of the process of apotransketolase interaction with thiamine diphosphate is affected by the regulatory activity of the donor substrate?

The interaction of thiamine diphosphate (ThDP) with transketolase (TK) involves at least two stages: [formula: see text] During the first stage, an inactive intermediate complex (TK...ThDP) is formed, which is then transformed into a catalytically active holoenzyme (TK* - ThDP). The second stage is related to conformational changes of the protein. In the preceding publication (Esakova, O. A., Meshalkina, L. E., Golbik, R., Hübner, G., and Kochetov, G. A. Eur. J. Biochem. 2004, 271, 4189 - 4194) we reported that the affinity of ThDP for TK considerably increases in the presence of the donor substrate, which may be a mechanism whereby the activity of the enzyme is regulated under the conditions of the coenzyme deficiency. Here, we demonstrate that the substrate affects the stage of the reverse conformational transition, characterized by the constant k(-1): in the presence of the substrate, its value is decreased several fold, whereas K(d) and k(+1) remain unchanged.     

Which circulating level of 25-hydroxyvitamin D is appropriate?

Moderate Vitamin D deficiency causes secondary hyperparathyroidism and bone loss, leading to osteoporosis and fractures. Controversy exists which circulating level of 25-hydroxyvitamin D (25OH)D is appropriate. The high incidence of hip fractures at northern latitudes suggest a relationship with Vitamin D deficiency. However, international studies show lower serum 25(OH)D levels in southern than in northern Europe. Serum 25(OH)D was not a risk factor for hip fractures in several epidemiological studies. The required serum 25(OH)D is usually established by assessing the point where serum parathyroid hormone (PTH) starts to rise. This point varied in several studies between 30 and 78 nmol/l. However, interlaboratory variation may also influence the apparent required serum 25(OH)D level. Dietary calcium intake influences serum PTH and serum PTH may influence the turnover of Vitamin D metabolites. A low calcium intake causes an increase of serum PTH and serum 1,25(OH)2D thereby decreasing the half life of serum 25(OH)D. While a low calcium intake may aggravate Vitamin D deficiency, a high calcium intake may have a Vitamin D sparing effect. With current knowledge, a global estimate for the appropriate serum 25(OH)D is 50 nmol/l.     

Which component of sulphasalazine is active in rheumatoid arthritis?

Sulphasalazine is known to be effective as a second line agent in the treatment of rheumatoid arthritis. The two chemical constituents of sulphasalazine (sulphapyridine and 5-aminosalicylic acid) were assessed separately in the treatment of rheumatoid arthritis. Over 24 weeks sulphapyridine showed a pronounced second line effect comparable with sulphasalazine and with a similar toxicity profile, whereas 5-aminosalicylic acid showed only a weak first line effect. Thus sulphapyridine appears to be the active moiety responsible for the second line effect of sulphasalazine in rheumatoid arthritis. The efficacy of the antibacterial component of sulphasalazine yet again permits speculation about the role of a bacterial pathogen in the aetiopathogenesis of rheumatoid disease.     

Which portion of the natural panorama is used for view-based navigation in the Australian desert ant?

Ants that forage in visually rich environments often develop idiosyncratic routes between their nest and a profitable foraging ground. Such route knowledge is underpinned by an ability to use visual landmarks for guidance and place recognition. Here we ask which portions of natural visual scenes are essential for visually guided navigation in the Australian desert ant Melophorus bagoti whose foragers navigate through a habitat containing grass tussocks, shrubs and trees. We captured M. bagoti foragers after they had returned to their nest from a feeder, but before they had entered their nest, and tested their ability to home accurately from a series of release locations. We used this simple release paradigm to investigate visually guided navigation by monitoring the accuracy of nestwards orientation when parts of the ants’ visual field were obscured. Results show that the lower portion of the visual panorama is more important for visually guided homing than upper portions. Analysis of panoramic images captured from the release and nest locations support the hypothesis that the important visual information is provided by the panoramic contour, where terrestrial objects contrast against sky, rather than by a limited number of salient landmarks such as tall trees.     

Plant preference for ammonium versus nitrate: a neglected determinant of ecosystem functioning?

Although nitrogen (N) availability is a major determinant of ecosystem properties, little is known about the ecological importance of plants' preference for ammonium versus nitrate (β) for ecosystem functioning and the structure of communities. We modeled this preference for two contrasting ecosystems and showed that β significantly affects ecosystem properties such as biomass, productivity, and N losses. A particular intermediate value of β maximizes the primary productivity and minimizes mineral N losses. In addition, contrasting β values between two plant types allow their coexistence, and the ability of one type to control nitrification modifies the patterns of coexistence with the other. We also show that species replacement dynamics do not lead to the minimization of the total mineral N pool nor the maximization of plant productivity, and consequently do not respect Tilman's R* rule. Our results strongly suggest in the two contrasted ecosystems that β has important consequences for ecosystem functioning and plant community structure.     

Which side of the π-macrocycle plane of (bacterio)chlorophylls is favored for binding of the fifth ligand?

Reported crystallographic data and calculated molecular models indicated that chlorophyll (Chl) a and bacteriochlorophyll (BChl) a tend to bind the fifth ligand on the side of the macrocycle where the C13²-(R)-methoxycarbonyl moiety protrudes (denoting the ‘back’ side). The crystal structures of 34 photosynthetic proteins possessing (B)Chl cofactors revealed that most of Chl a and BChl a (and b) are coordinated by any peptidyl residue (e.g., histydyl-imidazolyl group), peptidyl backbone or water from the ‘back’ side. Almost all the cofactors that bind a water molecule as the fifth ligand in these proteins have a ‘back’ configuration. Theoretical model calculations for methyl chlorophyllide a (MeChlid a) and methyl bacteriochlorophyllide a (MeBChlid a) bound to an imidazole molecule indicated that the ‘back’ side is energetically favored for the ligand binding. These results are consistent with the fact that ethyl chlorophyllide a (EtChlid a) dihydrate crystal consists of the ‘back’ complex. The modeling also showed that both removal and stereochemical inverse of the C13²-methoxycarbonyl group affect the relative stability between the ‘back’ and ‘face’ complexes. The effect of the C13²-moiety on the choice of the macrocycle side for the ligand binding is discussed in relation to the function of P700. This revised version was published online in June 2006 with corrections to the Cover Date.     

Which phase of the contraction-relaxation cycle of cytoplasmic actomyosin in Physarum is modulated by blue light?

The influence of blue-green light (496 nm) and blue light (450 nm) on contraction behaviour of protoplasmic strands, endoplasmic veins and “de novo” generation of contraction activity in endoplasmic drops of Physarum polycephalum was investigated. The contraction-relaxation cycle was divided into contraction (t_c) and relaxation (t_r) and separately analysed. Both wavelengths prolongated only the duration of contraction, whereas the duration of relaxation remained unaffected. The effect is quantitatively the same for endoplasmic veins and protoplasmic strands and is more pronounced in the case of blue light (450 nm).Blue light shows not only an influence on the duration of contraction but also on the time point of “de novo” generation of oscillatory activity of endoplasmic drops. Since blue light reversibly inhibits both glucose consumption and acidification of the medium, the obtained results point to a modification of the contraction phase via energy metabolism. However, the influence of a plasmalemmal proton pump has also to be taken into account.     

Which Copper is Paramagnetic in the Type 2/Type 3 Cluster of Laccase?

 Understanding the structure and function of the three copper atoms in the dioxygen reduction site of the blue oxidases such as laccase has been a long standing challenge. In the case of a widely studied derivative, known as type 2-depleted laccase, the removal of one copper from the cluster abolishes the EPR signal of the so-called type 2 copper. However, the present studies of isotopically enriched protein from Polyporus versicolor show that the readily replaceable copper is not active in the low-temperature EPR spectrum of fungal laccase or its difluoride adduct. The same is true for the difluoride adduct of the tree enzyme. Thus, in type 2-depleted laccase the pattern of antiferromagnetic coupling is quite different from that of the native protein or the difluoride adduct. Received: 5 October 1998 / Accepted: 13 January 1999