Effects of Post-Anthesis High-Temperature Stress on Carbon Partitioning and Starch Biosynthesis in a Spring Wheat (Triticum aestivum L.) Adapted to Moderate Growth Temperatures.

This study investigates carbon partitioning in the developing endosperm of a European variety of spring wheat subjected to moderately elevated daytime temperatures (27°C/16°C d/night) from anthesis to grain maturity. Elevated daytime temperatures caused significant reductions in both fresh and dry weights and reduced the starch content of harvested grains compared to plants grown under a 20°C/16°C d/night regimen. Accelerated grain development caused by elevated temperatures was accounted for by representing plant development as thermal time (°C DPA). We examined the effects of high-temperature stress (HTS) on the uptake and partitioning of [U-14C]-sucrose supplied to isolated endosperms. HTS caused reduced sucrose uptake into developing endosperms from the second major grain-filling stage (approximately 260°C DPA) up to maturity. Enzymes involved in sucrose metabolism were unaffected by HTS, whereas key enzyme activities involved in endosperm starch deposition such as ADP-glucose pyrophosphorylase and soluble isoforms of starch synthase were sensitive to HTS throughout grain development. HTS caused a decrease in other major carbon sinks such as evolved CO2, ethanol-soluble material, cell walls and protein. Despite reductions in the labeling of carbon pools caused by HTS, the relative proportions of sucrose taken up by endosperm cells allocated to each cellular pool remain unchanged, except for evolved CO2, which increased under HTS and may reflect enhanced respiratory activity. The results of this study show that moderate temperature increases can cause significant yield reductions in some temperate wheat cultivars chiefly through three effects: reduced sucrose uptake by the endosperm, reduced starch synthesis and increased partitioning of carbon into evolved CO2.

A mathematical model for simulating the spread of a disease through a country divided into geographical regions with different population densities.

The SIR (susceptible-infectious-recovered) model is a well known method for predicting the number of people (or animals) in a population who become infected by and then recover from a disease. Modifications can include categories such people who have been exposed to the disease but are not yet infectious or those who die from the disease. However, the model has nearly always been applied to the entire population of a country or state but there is considerable observational evidence that diseases can spread at different rates in densely populated urban regions and sparsely populated rural areas. This work presents a new approach that applies a SIR type model to a country or state that has been divided into a number of geographical regions, and uses different infection rates in each region which depend on the population density in that region. Further, the model contains a simple matrix based method for simulating the movement of people between different regions. The model is applied to the spread of disease in the United Kingdom and the state of Rio Grande do Sul in Brazil.

Severe hepatic dysfunction is associated with venous thromboembolic events in phase 1 clinical trials.

INTRODUCTION: Venous thromboembolic events (VTEs) are a significant cause of death in patients with cancer. The incidence of VTE is not well characterized in early phase clinical trials of novel antineoplastic agents, or in hepatic dysfunction studies designed for patients with varying degrees of liver test abnormalities. We compared the incidences of VTE in phase 1 clinical trials (P1CTs) and hepatic dysfunction trials (HDCTs) sponsored by the Cancer Therapy Evaluation Program of the National Cancer Institute (NCI) of the United States. MATERIALS & METHODS: We reviewed individual patient records of 1841 subjects for symptomatic VTE diagnosed while on study: 1328 subjects on 42 P1CTs, and 513 subjects on 9 HDCTs. The NCI's Organ Dysfunction Working Group definitions were used to categorize patients. The incidences of VTEs between patients were compared by the Chi square test. Confounders were evaluated with the Cochran-Mantel-Haenszel method. RESULTS & CONCLUSIONS: There were 43 VTEs identified among all subjects (2.3%). There were significantly more VTE observed in the subjects on P1CTs (n=38, 2.9%) than in the subjects on HDCTs (n=5, 1.0%; RR 0.341, 95% 0.13-0.86, p=0.015). For patients on HDCTs, those with severe dysfunction had a high incidence of VTE (RR 10.5 (1.12-93.6), p=0.021) that remained significant in a multivariate model. VTEs were observed less frequently in patients who were enrolled in HDCT than those who were enrolled in P1CT; however, patients with severe hepatic dysfunction were more likely to experience VTE. Severe liver test abnormalities may not be protective against VTE in patients with malignancies receiving chemotherapy.

The role of age on dose-limiting toxicities in phase I dose-escalation trials.

PURPOSE: Elderly oncology patients are not enrolled in early-phase trials in proportion to the numbers of geriatric patients with cancer. There may be concern that elderly patients will not tolerate investigational agents as well as younger patients, resulting in a disproportionate number of dose-limiting toxicities (DLT). Recent single-institution studies provide conflicting data on the relationship between age and DLT. EXPERIMENTAL DESIGN: We retrospectively reviewed data about patients treated on single-agent, dose-escalation, phase I clinical trials sponsored by the Cancer Therapy Evaluation Program (CTEP) of the National Cancer Institute. Patients' dose levels were described as a percentage of maximum tolerated dose, the highest dose level at which <33% of patients had a DLT, or recommended phase II dose (RP2D). Mixed-effect logistic regression models were used to analyze relationships between the probability of a DLT and age and other explanatory variables. RESULTS: Increasing dose, increasing age, and worsening performance status (PS) were significantly related to an increased probability of a DLT in this model (P < 0.05). There was no association between dose level administered and age (P = 0.57). CONCLUSIONS: This analysis of phase I dose-escalation trials, involving more than 500 patients older than 70 years of age, is the largest reported. As age and dose level increased and PS worsened, the probability of a DLT increased. Although increasing age was associated with occurrence of DLT, this risk remained within accepted thresholds of risk for phase I trials. There was no evidence of age bias on enrollment of patients on low or high dose levels.

Degradation of lignified secondary cell walls of lucerne (Medicago sativa L.) by rumen fungi growing in methanogenic co-culture.

AIMS: To compare the abilities of the monocentric rumen fungi Neocallimastix frontalis, Piromyces communis and Caecomyces communis, growing in coculture with Methanobrevibacter smithii, to colonize and degrade lignified secondary cell walls of lucerne (alfalfa) hay. METHODS AND RESULTS: The cell walls of xylem cylinders isolated from stems of lucerne contained mostly xylans, cellulose and lignin together with a small proportion of pectic polysaccharides. All of these major components were removed during incubation with the three fungi, and differing cell wall polysaccharides were degraded to different extents. The greatest dry weight loss was found with N. frontalis and least with C. communis, and scanning electron microscopy revealed that these extensively colonized different cell types. C. communis specifically colonized secondary xylem fibres and showed much less degradation than N. frontalis and P. communis. CONCLUSIONS: Neocallimastix frontalis and P. communis were efficient degraders of the cell walls of lucerne xylem cylinders. Degradation occurred of pectic polysaccharides, xylan and cellulose. Loss of lignin from the xylem cylinders probably resulted from the cleavage of xylan releasing xylan-lignin complexes. SIGNIFICANCE AND IMPACT OF THE STUDY: Unlike rumen bacteria, the rumen fungi N. frontalis, P. communis and C. communis are able to degrade lignified secondary walls in lucerne stems. These fungi could improve forage utilization by ruminants and may have potential in the degradation of lignocellulosic biomass in the production of biofuels.

Tuning the self-assembly of the bioactive dipeptide L-carnosine by incorporation of a bulky aromatic substituent.

The dipeptide L-carnosine has a number of important biological properties. Here, we explore the effect of attachment of a bulky hydrophobic aromatic unit, Fmoc [N-(fluorenyl-9-methoxycarbonyl)] on the self-assembly of Fmoc-L-carnosine, i.e., Fmoc-ß-alanine-histidine (Fmoc-ßAH). It is shown that Fmoc-ßAH forms well-defined amyloid fibrils containing ß sheets above a critical aggregation concentration, which is determined from pyrene and ThT fluorescence experiments. Twisted fibrils were imaged by cryogenic transmission electron microscopy. The zinc-binding properties of Fmoc-ßAH were investigated by FTIR and Raman spectroscopy since the formation of metal ion complexes with the histidine residue in carnosine is well-known, and important to its biological roles. Observed changes in the spectra may reflect differences in the packing of the Fmoc-dipeptides due to electrostatic interactions. Cryo-TEM shows that this leads to changes in the fibril morphology. Hydrogelation is also induced by addition of an appropriate concentration of zinc ions. Our work shows that the Fmoc motif can be employed to drive the self-assembly of carnosine into amyloid fibrils.

A Burton-Miller inverse boundary element method for near-field acoustic holography.

An inverse boundary element method based on the Burton-Miller integral equation is proposed for reconstructing the Neumann boundary data from pressure values on a conformal surface in the near-field of an arbitrary radiating object. The accuracy of the reconstruction is compared with that of a method based on the more commonly used Helmholtz integral equation. In particular, the behavior at characteristic frequencies, which are known to be problematic in the Helmholtz integral equation for the forward problem, is examined. The effect of regularization is considered, including the L-curve parameter selection method. Numerical computations are given for noisy data generated from an internal point source.

Influence of the solvent on the self-assembly of a modified amyloid beta peptide fragment. I. Morphological investigation.

The solvent-induced transition between self-assembled structures formed by the peptide AAKLVFF is studied via electron microscopy, light scattering, and spectroscopic techniques. The peptide is based on a core fragment of the amyloid beta-peptide, KLVFF, extended by two alanine residues. AAKLVFF exhibits distinct structures of twisted fibrils in water or nanotubes in methanol. For intermediate water/methanol compositions, these structures are disrupted and replaced by wide filamentous tapes that appear to be lateral aggregates of thin protofilaments. The orientation of the beta-strands in the twisted tapes or nanotubes can be deduced from X-ray diffraction on aligned stalks, as well as FT-IR experiments in transmission compared to attenuated total reflection. Strands are aligned perpendicular to the axis of the twisted fibrils or the nanotubes. The results are interpreted in light of recent results on the effect of competitive hydrogen bonding upon self-assembly in soft materials in water/methanol mixtures.

Self-assembly in aqueous solution of a modified amyloid beta peptide fragment.

The self-assembly in films dried from aqueous solutions of a modified amyloid beta peptide fragment is studied. We focus on sequence Abeta(16-20), KLVFF, extended by two alanines at the N-terminus to give AAKLVFF. Self-assembly into twisted ribbon fibrils is observed, as confirmed by transmission electron microscopy (TEM). Dynamic light scattering reveals the semi-flexible nature of the AAKLVFF fibrils, while polarized optical microscopy shows that the peptide fibrils crystallize after an aqueous solution of AAKLVFF is matured over 5 days. The secondary structure of the fibrils is studied by FT-IR, circular dichroism and X-ray diffraction (XRD), which provide evidence for beta-sheet structure in the fibril. From high resolution TEM it is concluded that the average width of an AAKLVFF fibril is (63+/-18) nm, indicating that these fibrils comprise beta-sheets with multiple repeats of the unit cell, determined by XRD to have b and c dimensions 1.9 and 4.4 nm with an a axis 0.96 nm, corresponding to twice the peptide backbone spacing in the antiparallel beta-sheet.

Degradation of forage chicory by ruminal fibrolytic bacteria.

AIMS: Determine the susceptibility of forage chicory (Cichorium intybus L.) to degradation by ruminal fibrolytic bacteria and measure the effects on cell-wall pectic polysaccharides. METHODS AND RESULTS: Large segments of fresh forage chicory were degraded in vitro by Lachnospira multiparus and Fibrobacter succinogenes, but not by Ruminococcus flavefaciens or Butyrivibrio hungatei. Cell-wall pectins were degraded extensively (95%) and rapidly by L. multiparus with a simultaneous release of uronic acids and the pectin-derived neutral monosaccharides arabinose, galactose and rhamnose. Fibrobacter succinogenes also degraded cell-wall pectins extensively, but at a slower rate than L. multiparus. Immunofluorescence microscopy using monoclonal antibodies revealed that, after incubation, homogalacturonans with both low and high degrees of methyl esterification were almost completely lost from walls of all cell types and from the middle lamella between cells. CONCLUSIONS: Only two of the four ruminal bacteria with pectinolytic activity degraded fresh chicory leaves, and each showed a different pattern of pectin breakdown. Degradation was greatest for F. succinogenes which also had cellulolytic activity. SIGNIFICANCE AND IMPACT OF THE STUDY: The finding of extensive removal of pectic polysaccharides from the middle lamella and the consequent decrease in particle size may explain the decreased rumination and the increased intake observed in ruminants grazing forage chicory.

Self-assembly of Peptide nanotubes in an organic solvent.

The self-assembly of a modified fragment of the amyloid beta peptide, based on sequence Abeta(16-20), KLVFF, extended to give AAKLVFF is studied in methanol. Self-assembly into peptide nanotubes is observed, as confirmed by electron microscopy and small-angle X-ray scattering. The secondary structure of the peptide is probed by FTIR and circular dichroism, and UV/visible spectroscopy provides evidence for the important role of aromatic interactions between phenylalanine residues in driving beta-sheet self-assembly. The beta-sheets wrap helically to form the nanotubes, the nanotube wall comprising four wrapped beta-sheets. At higher concentration, the peptide nanotubes form a nematic phase that exhibits spontaneous flow alignment as observed by small-angle neutron scattering.

Quantitative phase amplitude microscopy IV: imaging thick specimens.

The ability to image phase distributions with high spatial resolution is a key capability of microscopy systems. Consequently, the development and use of phase microscopy has been an important aspect of microscopy research and development. Most phase microscopy is based on a form of interference. Some phase imaging techniques, such as differential interference microscopy or phase microscopy, have a low coherence requirement, which enables high-resolution imaging but in effect prevents the acquisition of quantitative phase information. These techniques are therefore used mainly for phase visualization. On the other hand, interference microscopy and holography are able to yield quantitative phase measurements but cannot offer the highest resolution. A new approach to phase microscopy, quantitative phase-amplitude microscopy (QPAM) has recently been proposed that relies on observing the manner in which intensity images change with small defocuses and using these intensity changes to recover the phase. The method is easily understood when an object is thin, meaning its thickness is much less than the depth of field of the imaging system. However, in practice, objects will not often be thin, leading to the question of what precisely is being measured when QPAM is applied to a thick object. The optical transfer function formalism previously developed uses three-dimensional (3D) optical transfer functions under the Born approximation. In this paper we use the 3D optical transfer function approach of Streibl not for the analysis of 3D imaging methods, such as tomography, but rather for the problem of analysing 2D phase images of thick objects. We go on to test the theoretical predictions experimentally. The two are found to be in excellent agreement and we show that the 3D imaging properties of QPAM can be reliably predicted using the optical transfer function formalism.

Effect of drought stress on the yield and composition of volatile oils of drought-tolerant and non-drought-tolerant clones of Tagetes minuta.

A drought-tolerant clone of Tagetes minuta L. (Asteraceae) was selected in vitro on a medium containing 60 mM mannitol. In the greenhouse, a decrease in soil field capacity (FC) from 100 to 40 % reduced oil yield by 49, 71 and 71 % for drought-tolerant, non-drought tolerant cloned and seed-grown plants, respectively. In soil at 40 % FC, the drought-tolerant clone had the highest leaf dry weight and oil yield. At 100 % FC, there was no significant difference in leaf dry weight, but the drought-tolerant clone had a significantly higher percentage oil content and yield than seed-grown plants. The main components of the oil were monoterpenes of which trans- and cis-tagetone together were 52.3 % - 64.2 %. Drought significantly altered the content of some oil components.

Arbuscular mycorrhizal fungi confer enhanced arsenate resistance on Holcus lanatus.

• The role of arbuscular mycorrhizal fungi (AMF) in arsenate resistance in arbuscular mycorrhizal associations is investigated here for two Glomus spp. isolated from the arsenate-resistant grass Holcus lanatus. • Glomus mosseae and Glomus caledonium were isolated from H. lanatus growing on an arsenic-contaminated mine-spoil soil. The arsenate resistance of spores was compared with nonmine isolates using a germination assay. Short-term arsenate influx into roots and long-term plant accumulation of arsenic by plants were also investigated in uninfected arsenate resistant and nonresistant plants and in plants infected with mine and nonmine AMF. • Mine AMF isolates were arsenate resistant compared with nonmine isolates. Resistant and nonresistant G. mosseae both suppressed high-affinity arsenate/phosphate transport into the roots of both resistant and nonresistant H. lanatus. Resistant AMF colonization of resistant H. lanatus growing in contaminated mine spoil reduced arsenate uptake by the host. • We conclude that AMF have evolved arsenate resistance, and conferred enhanced resistance on H. lanatus.

Experimental determination of the diffusion coefficient in two-dimensions in ferrous sulphate gels using the finite element method.

A novel two-dimensional finite element method for modelling the diffusion which occurs in Fricke or ferrous sulphate type radiation dosimetry gels is presented. In most of the previous work, the diffusion coefficient has been estimated using simple one-dimensional models. This work presents a two-dimensional model which enables the diffusion coefficient to be determined in a much wider range of experimental situations. The model includes the provision for the determination of a drift parameter. To demonstrate the technique comparative diffusion measurements between ferrous sulphate radiation dosimetry gels, with and without xylenol orange chelating agent and carbohydrate additives have been undertaken. Diffusion coefficients of 9.7 +/- 0.4, 13.3 +/- 0.6 and 9.5 +/- 0.8 10(-3) cm2h-1 were determined for ferrous sulphate radiation dosimetry gels with and without xylenol orange and with xylenol orange and sucrose additives respectively.

Ferulic acid is esterified to glucuronoarabinoxylans in pineapple cell walls.

The ester-linkage of ferulic acid (mainly E) to polysaccharides in primary cell walls of pineapple fruit (Ananas comosus) (Bromeliaceae) was investigated by treating a cell-wall preparation with 'Driselase' which contains a mixture of endo- and exo-glycanases, but no hydroxycinnamoyl esterase activity. The most abundant feruloyl oligosaccharide released was O-[5-O-(E-feruloyl)-alpha-L-arabinofuranosyl](1-->3)-O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose (FAXX). This indicated that the ferulic acid is ester-linked to glucuronoarabinoxylans in the same way as in the primary walls of grasses and cereals (Poaceae). Glucuronoarabinoxylans are the major non-cellulosic polysaccharides in the pineapple cell walls.

In vitro proximal tubule perfusion preparation.

Isolation and perfusion of single nephron segments was first described by Burg et al. (1) in 1966. This technique has allowed us to study both transepithelial and transmembrane transport in individual nephron segments, including the proximal tubule, under carefully controlled circumstances. This has obvious advantages for experiments that require the epithelium and its junctional complexes to remain intact, but removed from the influences of endogenous neural or humoral mediators, including angiotensins. In addition, control of bath and luminal perfusate compositions and flow rates allows peptides to be added independently to each side of the epithelium. This has particular relevance in the case of angiotensin, which binds to luminal and basolateral receptors and initiates intracellular signal transduction pathways that may differ between the two sites (2).

Impact of climate on thermal rhythm in pastoral sheep.

The effects of environmental conditions on temperature rhythms were investigated in ewe lambs at pasture. Two groups of 20 lambs had heart rate (HR), vaginal temperature (T(v)), ear-canal temperature (T(c)) and ear-pinna temperature (T(p)) monitored continuously for 3 days. Climatic conditions were recorded at the same time and Temperature Humidity Index (THI) calculated. One group experienced fine clear weather for the 3 days, the other group experienced 2 days of heavy rain. During periods of fine weather, the daily rhythm for T(v) and T(c) was monophasic. However, heavy rain and a constant THI reduced the amplitude of the recorded temperature rhythms. Daily T(v) and T(c) patterns correlated strongly with THI, with a phase lag of 2 h. Peak T(v) and T(c) were at approximately 17:00 h each day. Mean maximum daily amplitudes were approximately 1.3 degrees C for T(v) and T(c). Mean T(v) was 39.3+/-0.1 and 39.6+/-0.1 for weeks 1 and 2, respectively, while mean T(c) was 38.9+/-0.1 and 39.2+/-0.1. Changes in T(v) and T(c) were closely correlated. We conclude that climate has a major effect on body temperature rhythms.

Changing concepts of dietary fiber: implications for carcinogenesis.

The dietary fiber (DF) hypothesis suggested that DF, as plant cell walls, protected against colorectal cancer. The implicit assumption in much historic literature was that the readily analyzed and quantified nonstarch polysaccharide (NSP) component was critical in cancer protection. However, the presence of polymeric phenolic components such as lignin or suberin has profound effects on the physicochemical properties of the cell walls and largely determines their physiological properties in humans. In certain groups of food plants, degradation of cell walls that contain neither lignin nor suberin releases ferulic acid and other hydroxycinnamic acids. These acids have antioxidant, antimutagenic, and other anticancer effects, including modulation of gene expression and immune response. Reexamination of literature on cancer protection suggests that plant cell walls containing significant amounts of phenolic components may be the most likely to protect against cancer. In the last 30 years, the definition of DF has been incrementally expanded to incorporate NSP extracted from plant cell walls and from sources other than plant cell walls, then resistant starch, and most recently nondigestible oligosaccharides. On the early definitions, increased consumption of DF could only be achieved by increasing the intake of whole grains, brans, or other food plant material that would increase the intake of plant cell walls containing significant amounts of phenolic components. However, the new definitions make it possible to increase "dietary fiber" without consuming any such materials. We suggest that this could have negative connotations for cancer risk in human populations.