NMR studies of [1-2H]glucose metabolism in Zymomonas mobilis

In complementary experiments the metabolism of [1-2H]glucose in H2O and of unlabelled glucose in 2H2O by Zymomonas mobilis was examined. The utilization of [1-2H]glucose by Z. mobilis was monitored by high-resolution 2H NMR. The deuterium-labelling pattern and stereochemistry of the ethanols produced from the metabolism of [1-2H]glucose and unlabelled glucose in 2H2O were determined by a combination of 13C and 1H NMR and selective enzyme action. The labelling patterns were explained in terms of enzyme mechanisms and stereospecificity, and metabolite enolization.     

Large vesicle contamination in small,unilamellar vesicles

Small, unilamellar phospholipid vesicles have been prepared using a new, high-powdered cup sonifier that avoids contact of the sample with a titanium probe. These vesicles have been characterized by gel filtration chromatography both before and after fractionation by high-speed centrifugation. Plots of the turbidity of centrifuged vesicles between 300 and 650 nm against the reciprocal fourth power of the scattering wavelength were linear with zero intercepts (extrapolated to infinite wavelength). In the presence of minute quantities of large, multilamellar vesicles, these plots remained linear but had intercepts quantitatively proportional to the amount of contaminating large vesicles. Since this measurement requires only a standard spectrophotometer and very small quantities of lipid, this method is suggested as a useful assay for determining contamination of small vesicle preparations by large vesicles. Two applications of this method as well as a practical limitation are discussed.     

A tritrophic signal that attracts parasitoids to host-damaged plants withstands disruption by non-host herbivores

Background  

Volatiles emitted by herbivore-infested plants are highly attractive to parasitoids and therefore have been proposed to be part of an indirect plant defense strategy. However, this proposed function of the plant-provided signals remains controversial, and it is unclear how specific and reliable the signals are under natural conditions with simultaneous feeding by multiple herbivores. Phloem feeders in particular are assumed to interfere with plant defense responses. Therefore, we investigated how attack by the piercing-sucking cicadellid Euscelidius variegatus influences signaling by maize plants in response to the chewing herbivore Spodoptera littoralis.     

Haplotype Analysis of Hemochromatosis: Evaluation of Different Linkage-Disequilibrium Approaches and Evolution of Disease Chromosomes

We applied several types of linkage-disequilibrium calculations to analyze the hereditary hemochromatosis (hh) locus. Twenty-four polymorphic markers in the major histocompatibility complex (MHC) class I region were used to haplotype hh and normal chromosomes. A total of 169 hh and 161 normal chromosomes were analyzed. Disequilibrium values were found to be high over an unusually large region beginning 150 kb centro-meric of HLA-A and extending nearly 5 Mb telomeric of it. Recombination in this region was −28% of the expected value. This low level of recombination contributes to the unusually broad region of linkage disequilibrium found with hh. The strongest disequilibrium was found at locus HLA-H (d = .84) and at locus D6S2239 (d = .85), a marker −10 kb telomeric to HLA-H. All disequilibrium methods employed in this study found peak disequilibrium at HLA-H or D6S2239. The cys282tyr mutation in HLA-H, a candidate gene for hh, was found in 85% of disease chromosomes. A haplotype phylogeny for hh chromosomes was constructed and suggests that the mutation associated with the most common haplotype occurred relatively recently. The age of the hh mutation was estimated to be −60-70 generations. Disequilibrium was maintained over a greater distance for hh-carrying chromosomes, consistent with a recent mutation for hh. Our data provide a reasonable explanation for previous difficulties in localizing the hh locus and provide an evolutionary history for disease chromosomes.     

Measurement of the effects of pH on phosphate availability

Plant and Soil - Many soil scientists think that soil phosphate availability is highest at near-neutral pH and decreases with decreasing pH. This belief does not appear to have ever been subjected...     

Pharmacological inhibition of GSK-3 in a guinea pig model of LPS-induced pulmonary inflammation: II. Effects on skeletal muscle atrophy

Background

Chronic obstructive pulmonary disease (COPD) is accompanied by pulmonary inflammation and associated with extra-pulmonary manifestations, including skeletal muscle atrophy. Glycogen synthase kinase-3 (GSK-3) has been implicated in the regulation of muscle protein- and myonuclear turnover; two crucial processes that determine muscle mass. In the present study we investigated the effect of the selective GSK-3 inhibitor SB216763 on muscle mass in a guinea pig model of lipopolysaccharide (LPS)-induced pulmonary inflammation-associated muscle atrophy.

Methods

Guinea pigs were pretreated with either intranasally instilled SB216763 or corresponding vehicle prior to each LPS/saline challenge twice weekly. Pulmonary inflammation was confirmed and indices of muscle mass were determined after 12 weeks. Additionally, cultured skeletal muscle cells were incubated with tumor necrosis factor α (TNF-α) or glucocorticoids (GCs) to model the systemic effects of pulmonary inflammation on myogenesis, in the presence or absence of GSK-3 inhibitors.

Results

Repeated LPS instillation induced muscle atrophy based on muscle weight and muscle fiber cross sectional area. Intriguingly, GSK-3 inhibition using SB216763 prevented the LPS-induced muscle mass decreases and myofiber atrophy. Indices of protein turnover signaling were unaltered in guinea pig muscle. Interestingly, inhibition of myogenesis of cultured muscle cells by TNF-α or synthetic GCs was prevented by GSK-3 inhibitors.

Conclusions

In a guinea pig model of LPS-induced pulmonary inflammation, GSK-3 inhibition prevents skeletal muscle atrophy without affecting pulmonary inflammation. Resistance to inflammation- or GC-induced impairment of myogenic differentiation, imposed by GSK-3 inhibition, suggests that sustained myogenesis may contribute to muscle mass maintenance despite persistent pulmonary inflammation. Collectively, these results warrant further exploration of GSK-3 as a potential novel drug target to prevent or reverse muscle wasting in COPD.     

Structure–activity relationship for enantiomers of potent inhibitors of B. anthracis dihydrofolate reductase

Background: Bacterial resistance to antibiotic therapies is increasing and new treatment options are badly needed. There is an overlap between these resistant bacteria and organisms classified as likely bioterror weapons. For example, Bacillus anthracis is innately resistant to the anti-folate trimethoprim due to sequence changes found in the dihydrofolate reductase enzyme. Development of new inhibitors provides an opportunity to enhance the current arsenal of anti-folate antibiotics while also expanding the coverage of the anti-folate class. Methods: We have characterized inhibitors of B. anthracis dihydrofolate reductase by measuring the K_i and MIC values and calculating the energetics of binding. This series contains a core diaminopyrimidine ring, a central dimethoxybenzyl ring, and a dihydrophthalazine moiety. We have altered the chemical groups extended from a chiral center on the dihydropyridazine ring of the phthalazine moiety. The interactions for the most potent compounds were visualized by X-ray structure determination. Results: We find that the potency of individual enantiomers is divergent with clear preference for the S-enantiomer, while maintaining a high conservation of contacts within the binding site. The preference for enantiomers seems to be predicated largely by differential interactions with protein residues Leu29, Gln30 and Arg53. Conclusions: These studies have clarified the activity of modifications and of individual enantiomers, and highlighted the role of the less-active R-enantiomer in effectively diluting the more active S-enantiomer in racemic solutions. This directly contributes to the development of new antimicrobials, combating trimethoprim resistance, and treatment options for potential bioterrorism agents.     

Wnt/planar cell polarity signaling: an important mechanism to coordinate growth and patterning in the limb

The limb is one of the premier models for studying how a simple embryonic anlage develops into complex three-dimensional form. One of the key issues in the limb field has been to determine how the limb becomes patterned along its proximal (shoulder/hip) to distal (digits) axis. For decades it has been known that the apical ectodermal ridge (AER) plays a crucial role in distal outgrowth and patterning of the vertebrate embryonic limb. Most studies have explored the relationship between the AER and the progressive assignment of cell fates to mesenchyme along the proximal to distal (PD) axis. Comparatively few, however, have examined the additional role of the AER to regulate distal outgrowth of the limb and how this growth may also influence pattern along the PD axis. Here, I will review key studies that explore the role of growth in limb development. In particular, I will focus on a recent flurry of papers that examine the role of the Wnt/planar cell polarity (PCP) pathway in regulating directed growth of the limb mesenchyme. Finally, I will discuss a potential mechanism that relates the AER to the Wnt/PCP pathway and how directed growth can play a role in shaping the limb along the PD axis.     

Indigo: an annotated bibliography

This bibliography lists and comments on publications describing the history, preparation, chemistry and some applications of indigo and related dyes. Note that the commentary by the author is in italics after the bibliographic information.