A molecular and structural characterization of senescing Arabidopsis siliques and comparison of transcriptional profiles with senescing petals and leaves

Senescence of plant organs is a genetically controlled process that regulates cell death to facilitate nutrient recovery and recycling, and frequently precedes, or is concomitant with, ripening of reproductive structures. In Arabidopsis thaliana, the seeds are contained within a silique, which is itself a photosynthetic organ in the early stages of development and undergoes a programme of senescence prior to dehiscence. A transcriptional analysis of the silique wall was undertaken to identify changes in gene expression during senescence and to correlate these events with ultrastructural changes. The study revealed that the most highly up-regulated genes in senescing silique wall tissues encoded seed storage proteins, and the significance of this finding is discussed. Global transcription profiles of senescing siliques were compared with those from senescing Arabidopsis leaf or petal tissues using microarray datasets and metabolic pathway analysis software (MapMan). In all three tissues, members of NAC and WRKY transcription factor families were up-regulated, but components of the shikimate and cell-wall biosynthetic pathways were down-regulated during senescence. Expression of genes encoding ethylene biosynthesis and action showed more similarity between senescing siliques and petals than between senescing siliques and leaves. Genes involved in autophagy were highly expressed in the late stages of death of all plant tissues studied, but not always during the preceding remobilization phase of senescence. Analyses showed that, during senescence, silique wall tissues exhibited more transcriptional features in common with petals than with leaves. The shared and distinct regulatory events associated with senescence in the three organs are evaluated and discussed.

Theoretical and experimental approaches towards the determination of solute effective diffusivities in foods

The aim of this review paper is to present experimental methodologies and the mathematical approaches used to determine effective diffusivities of solutes in food materials. The paper commences by describing the diffusion phenomena related to solute mass transfer in foods and effective diffusivities. It then focuses on the mathematical formulation for the calculation of effective diffusivities considering different diffusion models based on Fick's second law of diffusion. Finally, experimental considerations for effective diffusivity determination are elucidated primarily based on the acquirement of a series of solute content versus time curves appropriate to the equation model chosen. Different factors contributing to the determination of the effective diffusivities such as the structure of food material, temperature, diffusion solvent, agitation, sampling, concentration and different techniques used are considered. (c) 2005 Elsevier Inc. All rights reserved.

Velocity profiles and frictional pressure drop for shear thinning materials in lid-driven cavities with fully developed axial flow

A finite element numerical study has been carried out on the isothermal flow of power law fluids in lid-driven cavities with axial throughflow. The effects of the tangential flow Reynolds number (Re-U), axial flow Reynolds number (Re-W), cavity aspect ratio and shear thinning property of the fluids on tangential and axial velocity distributions and the frictional pressure drop are studied. Where comparison is possible, very good agreement is found between current numerical results and published asymptotic and numerical results. For shear thinning materials in long thin cavities in the tangential flow dominated flow regime, the numerical results show that the frictional pressure drop lies between two extreme conditions, namely the results for duct flow and analytical results from lubrication theory. For shear thinning materials in a lid-driven cavity, the interaction between the tangential flow and axial flow is very complex because the flow is dependent on the flow Reynolds numbers and the ratio of the average axial velocity and the lid velocity. For both Newtonian and shear thinning fluids, the axial velocity peak is shifted and the frictional pressure drop is increased with increasing tangential flow Reynolds number. The results are highly relevant to industrial devices such as screw extruders and scraped surface heat exchangers. (c) 2006 Elsevier Ltd. All rights reserved.

Casein and whey exert different effects on plasma amino acid profiles, gastrointestinal hormone secretion and appetite

Protein, generally agreed to be the most satiating macronutrient, may differ in its effects on appetite depending on the protein source and variation in digestion and absorption. We investigated the effects of two milk protein types, casein and whey, on food intake and subjective ratings of hunger and fullness, and on postprandial metabolite and gastrointestinal hormone responses. Two studies were undertaken. The first study showed that energy intake from a buffet meal ad libitum was significantly less 90 min after a 1700 kJ liquid preload containing 48 g whey, compared with an equivalent casein preload (P<0.05). In the second study, the same whey preload led to a 28 % increase in postprandial plasma amino acid concentrations over 3 h compared with casein (incremental area under the curve (iAUC), P<0.05). Plasma cholecystokinin (CCK) was increased by 60 % (iAUC, P<0.005), glucagon-like peptide (GLP)-1 by 65 % (iAUC, P<0.05) and glucose-dependent insulinotropic polypeptide by 36 % (iAUC, P<0.01) following the whey preload compared with the casein. Gastric emptying was influenced by protein type as evidenced by differing plasma paracetamol profiles with the two preloads. Greater subjective satiety followed the whey test meal (P<0.05). These results implicate post-absorptive increases in plasma amino acids together with both CCK and GLP-1 as potential mediators of the increased satiety response to whey and emphasise the importance of considering the impact of protein type on the appetite response to a mixed meal.

Linguistic heterogeneity in Williams syndrome

Williams syndrome (WS) is a rare genetic disorder resulting from a deletion on chromosome 7. A number of studies have shown that individuals with WS have a superior linguistic profile compared to their non-verbal abilities, however the evidence has been inconclusive, as many studies have disputed such a profile. The vast majority of studies on WS have assumed a single, homogeneous WS linguistic profile in order to support various theoretical viewpoints. The present study investigated the linguistic profiles of 5 individuals with WS on a number of standardized verbal measures and in conversational settings. The results indicated substantially variable performance in all aspects of the verbal domain, which supports the view that WS, linguistically, is a rather heterogeneous condition and this should be taken into consideration when referring to it in theoretical accounts of language acquisition and debates on modularity.

Tests of syntactic comprehension in aphasia: an investigation of task effects

Background: Consistency of performance across tasks that assess syntactic comprehension in aphasia has clinical and theoretical relevance. In this paper we add to the relatively sparse previous work on how sentence comprehension abilities are influenced by the nature of the assessment task. Aims: Our aims are: (1) to compare linguistic performance across sentence-picture matching, enactment, and truth-value judgement tasks; (2) to investigate the impact of pictorial stimuli on syntactic comprehension. Methods Procedures: We tested a group of 10 aphasic speakers (3 with fluent and 7 with non-fluent aphasia) in three tasks (Experiment 1): (i) sentence-picture matching with four pictures, (ii) sentence-picture matching with two pictures, and (iii) enactment. A further task of truth-value judgement was given to a subgroup of those speakers (n=5, Experiment 2). Similar sentence types across all tasks were used and included canonical (actives, subject clefts) and non-canonical (passives, object clefts) sentences. We undertook two types of analyses: (a) we compared canonical and non-canonical sentences in each task; (b) we compared performance between (i) actives and passives, (ii) subject and object clefts in each task. We examined the results of all participants as a group and as case-series. Outcomes Results: Several task effects emerged. Overall, the two-picture sentence-picture matching and enactment tasks were more discriminating than the four-picture condition. Group performance in the truth-value judgement task was similar to two-picture sentence-picture matching and enactment. At the individual level performance across tasks contrasted to some group results. Conclusions: Our findings revealed task effects across participants. We discuss reasons that could explain the diverse profiles of performance and the implications for clinical practice.

Free-amino acid profiles of thua nao, a Thai fermented soybean

Thua nao, a rich source of free-amino acids, is a fermented soybean, usually used as seasoning or flavouring enhancer in northern Thailand. Free-amino acids (FAA) of unfermented/cooked soybeans, thua nao, fermented by pure Bacillus subtilis TN51 (TNB51), and a naturally fermented product (TNMX), were investigated by pre-column derivatisation with 9-fluorenylmethyl chloroformate, followed by reversed-phase HPLC. Total FAA and essential amino acids were found at significantly higher concentrations in TNB51 thua nao than in TNMX thua nao (naturally fermented). Both fermented thua nao had much higher concentrations of FAA than had their unfermented counterparts. With respect to taste-enhancing FAA, typical bitter attributes of thua nao came mainly from hydrophobic and basic FAA, whereas an umami attribute came predominantly from acidic FAA.

Assessing the accuracy of a computerized decision support system for digoxin dosing in primary care: an observational study

Background: This study was carried out as part of a European Union funded project (PharmDIS-e+), to develop and evaluate software aimed at assisting physicians with drug dosing. A drug that causes particular problems with drug dosing in primary care is digoxin because of its narrow therapeutic range and low therapeutic index. Objectives: To determine (i) accuracy of the PharmDIS-e+ software for predicting serum digoxin levels in patients who are taking this drug regularly; (ii) whether there are statistically significant differences between predicted digoxin levels and those measured by a laboratory and (iii) whether there are differences between doses prescribed by general practitioners and those suggested by the program. Methods: We needed 45 patients to have 95% Power to reject the null hypothesis that the mean serum digoxin concentration was within 10% of the mean predicted digoxin concentration. Patients were recruited from two general practices and had been taking digoxin for at least 4 months. Exclusion criteria were dementia, low adherence to digoxin and use of other medications known to interact to a clinically important extent with digoxin. Results: Forty-five patients were recruited. There was a correlation of 0·65 between measured and predicted digoxin concentrations (P < 0·001). The mean difference was 0·12 μg/L (SD 0·26; 95% CI 0·04, 0·19, P = 0·005). Forty-seven per cent of the patients were prescribed the same dose as recommended by the software, 44% were prescribed a higher dose and 9% a lower dose than recommended. Conclusion: PharmDIS-e+ software was able to predict serum digoxin levels with acceptable accuracy in most patients.

Cell cycle profiles and expression of p21CIP1 and P27KIP1 during myocyte development

The ability of the cardiac myocyte to divide ceases shortly after birth. Thus, following severe injury, e.g., during myocardial infarction, the mature heart is unable to regenerate new tissue to replace the dead or damaged tissue. The identification of the molecules controlling the cessation of myocyte cell division may lead to therapeutic strategies which aim to re-populate the damaged myocardial area. Hence, we have determined the cell cycle profile, expressions and activities of the cyclin-dependent kinase inhibitors (CDKIs), p21CIP1 and p27KIP1, during rat ventricular myocyte development. Fluorescent activated cell sorting (FACS) analyses showed the percentage of S phase myocytes to be decreased significantly throughout development, concomitant with a significant increase in the percentage of G0/G1 and G2/M phase cells. The expression of p21CIP1 and p27KIP1 increased significantly throughout cardiac development and complexed differentially with a number of cyclins and CDKs. Furthermore, an adult myocyte extract reduced neonatal myocyte CDK2 kinase activity significantly (>30%, p<0.05) whereas immunodepletion of p21CIP1 from adult lysates restored CDK2 kinase activity. Thus, p21CIP1 and p27KIP1 may be important for the withdrawal of cardiac myocytes from the cell cycle and for maintaining the G0/G1 and G2/M phase blockades.

Vertical velocity variance and skewness in clear and cloud-topped boundary layers as revealed by Doppler lidar

In this paper, observations by a ground-based vertically pointing Doppler lidar and sonic anemometer are used to investigate the diurnal evolution of boundary-layer turbulence in cloudless, cumulus and stratocumulus conditions. When turbulence is driven primarily by surface heating, such as in cloudless and cumulus-topped boundary layers, both the vertical velocity variance and skewness follow similar profiles, on average, to previous observational studies of turbulence in convective conditions, with a peak skewness of around 0.8 in the upper third of the mixed layer. When the turbulence is driven primarily by cloud-top radiative cooling, such as in the presence of nocturnal stratocumulus, it is found that the skewness is inverted in both sign and height: its minimum value of around −0.9 occurs in the lower third of the mixed layer. The profile of variance is consistent with a cloud-top cooling rate of around 30Wm−2. This is also consistent with the evolution of the thermodynamic profile and the rate of growth of the mixed layer into the stable nocturnal boundary layer from above. In conditions where surface heating occurs simultaneously with cloud-top cooling, the skewness is found to be useful for diagnosing the source of the turbulence, suggesting that long-term Doppler lidar observations would be valuable for evaluating boundary-layer parametrization schemes. Copyright c 2009 Royal Meteorological Society

Theoretical investigation of infrared spectra and pocket dynamics of photodissociated carbonmonoxy myoglobin

Molecular dynamics simulations of the photodissociated state of carbonmonoxy myoglobin (MbCO) are presented using a fluctuating charge model for CO. A new three-point charge model is fitted to high-level ab initio calculations of the dipole and quadrupole moment functions taken from the literature. The infrared spectrum of the CO molecule in the heme pocket is calculated using the dipole moment time autocorrelation function and shows good agreement with experiment. In particular, the new model reproduces the experimentally observed splitting of the CO absorption spectrum. The splitting of 3–7 cm−1 (compared to the experimental value of 10 cm−1) can be directly attributed to the two possible orientations of CO within the docking site at the edge of the distal heme pocket (the B states), as previously suggested on the basis of experimental femtosecond time-resolved infrared studies. Further information on the time evolution of the position and orientation of the CO molecule is obtained and analyzed. The calculated difference in the free energy between the two possible orientations (Fe···CO and Fe···OC) is 0.3 kcal mol−1 and agrees well with the experimentally estimated value of 0.29 kcal mol−1. A comparison of the new fluctuating charge model with an established fixed charge model reveals some differences that may be critical for the correct prediction of the infrared spectrum and energy barriers. The photodissociation of CO from the myoglobin mutant L29F using the new model shows rapid escape of CO from the distal heme pocket, in good agreement with recent experimental data. The effect of the protein environment on the multipole moments of the CO ligand is investigated and taken into account in a refined model. Molecular dynamics simulations with this refined model are in agreement with the calculations based on the gas-phase model. However, it is demonstrated that even small changes in the electrostatics of CO alter the details of the dynamics.

Theoretical studies of the interface between water and Langmuir films of aliphatic alcohols

The interface between water and Langmuir films of long chain aliphatic molecules is investigated using accurate intermolecular potentials. The stabilities of various ice structures which could form at the interface are examined. Antiferroelectric ice is found to be the most stable, but this stability depends crucially on the first layer of water. Ferroelectric structures are found to collapse upon relaxation. Our model was not able to differentiate between the different nucleation properties of C31H63OH and C30H61OH. A better description of the alcohol–water interaction is probably required to account for this difference.