Biomedical subjects

Andrew Richardson

Publications and source records attributed to Andrew Richardson.

7 recordsLinked to original sources

PubMed2006

Cuticular permeance in relation to wax and cutin development along the growing barley (Hordeum vulgare) leaf.

The developing leaf three of barley provides an excellent model system for the direct determination of relationships between amounts of waxes and cutin and cuticular permeance. Permeance of the cuticle was assessed via the time-course of uptake of either toluidine blue or (14)C-labelled benzoic acid ([(14)C] BA) along the length of the developing leaf. Toluidine blue uptake only occurred within the region 0-25 mm from the point of leaf insertion (POLI). Resistance--the inverse of permeance--to uptake of [(14)C] BA was determined for four leaf regions and was lowest in the region 10-20 mm above POLI. At 20-30 and 50-60 mm above POLI, it increased by factors of 6 and a further 32, respectively. Above the point of emergence of leaf three from the sheath of leaf two, which was 76-80 mm above POLI, resistance was as high as at 50-60 mm above POLI. GC-FID/MS analyses of wax and cutin showed that: (1) the initial seven fold increase in cuticular resistance coincided with increase in cutin coverage and appearance of waxes; (2) the second, larger and final increase in cuticle resistance was accompanied by an increase in wax coverage, whereas cutin coverage remained unchanged; (3) cutin deposition in barley leaf epidermis occurred in parallel with cell elongation, whereas deposition of significant amounts of wax commenced as cells ceased to elongate.

Hordeum↗

PubMed2006

The short-term growth response to salt of the developing barley leaf.

Recent results concerning the short-term growth response to salinity of the developing barley leaf are reviewed. Plants were grown hydroponically and the growth response of leaf 3 was studied between 10 min and 5 d following addition of 100 mM NaCl to the root medium. The aim of the experiments was to relate changes in variables that are likely to affect cell elongation to changes in leaf growth. Changes in hormone content (ABA, cytokinins), water and solute relationships (osmolality, turgor, water potential, solute concentrations), gene expression (water channel), cuticle deposition, membrane potential, and transpiration were followed, while leaf elongation velocity was monitored. Leaf elongation decreased close to zero within seconds following addition of NaCl. Between 20 and 30 min after exposure to salt, elongation velocity recovered rather abruptly, to about 46% of the pre-stress level, and remained at the reduced rate for the following 5 d, when it reached about 70% of the level in non-stressed plants. Biophysical and physiological analyses led to three major conclusions. (i) The immediate reduction and sudden recovery in elongation velocity is due to changes in the water potential gradient between leaf xylem and peripheral elongating cells. Changes in transpiration, ABA and cytokinin content, water channel expression, and plasma membrane potential are involved in this response. (ii) Significant solute accumulation, which aids growth recovery, is detectable from 1 h onwards; growing and non-growing leaf regions and mesophyll and epidermis differ in their solute response. (iii) Cuticular wax density is not affected by short-term exposure to salt; transpirational changes are due to stomatal control.

Abscisic Acid↗

PubMed2006

MR thermometry-based feedback control of efficacy and safety in minimum-time thermal therapies: phantom and in-vivo evaluations.

The experimental validation of a model-based, thermal therapy control system which automatically and simultaneously achieves the specified efficacy and safety objectives of the treatment is reported. MR-thermometry measurements are used in real-time to control the power of a stationary, focused ultrasound transducer in order to achieve the desired treatment outcome in minimum time without violating the imposed safety constraints. Treatment efficacy is quantified in terms of the thermal dose delivered to the target. Normal tissue safety is ensured by automatically maintaining normal tissue temperature below the imposed limit in the user-specified locations. To reflect hardware limitations, constraints on the maximum applied power are also imposed. At the pretreatment stage, MR imaging and thermometry are used to localize the treatment target and identify thermal and actuation models. The results of phantom and canine experiments demonstrate that spatially-distributed, real-time MR temperature measurements enhance one's ability to robustly achieve the desired treatment outcome in minimum time without violating safety constraints. Post-treatment evaluation of the outcome using T2-weighted images of canine muscle showed good spatial correlation between the sonicated area and thermally damaged tissue.

Animals↗

PubMed2005

Cuticular wax deposition in growing barley (Hordeum vulgare) leaves commences in relation to the point of emergence of epidermal cells from the sheaths of older leaves.

In grasses, leaf cells divide and expand within the sheaths of older leaves, where the micro-environment differs from the open atmosphere. By the time epidermal cells are displaced into the atmosphere, they must have a functional cuticle to minimize uncontrolled water loss. In the present study, gas chromatography and scanning electron microscopy were used to follow cuticular wax deposition along the growing leaf three of barley (Hordeum vulgare L.). 1-Hexacosanol (C(26) alcohol) comprised more than 75% of extractable cuticular wax and was used as a marker for wax deposition. There was no detectable wax along the first 20 mm from the point of leaf insertion. Deposition started within the distal portion of the elongation zone (23-45 mm) and continued beyond the point of leaf emergence from the sheath of leaf two. The region where wax deposition commenced shifted towards more proximal (basal) positions when the point of leaf emergence was lowered by stripping back part of the sheath. When relative humidity in the shoot environment was elevated from 70% (standard growth conditions) to 92-96% for up to 4 days prior to analysis, wax deposition did not change significantly. The results show that cuticular waxes are deposited along the growing grass leaf independent of cell age or developmental stage. Instead, the reference point for wax deposition appears to be the point of emergence of cells into the atmosphere. The possibility of changes in relative humidity between enclosed and emerged leaf regions triggering wax deposition is discussed.

Hordeum↗

PubMed2003

Growth prediction in Class III patients using cluster and discriminant function analysis.

This longitudinal retrospective cephalometric study was undertaken in an attempt to identify subgroups of subjects with Class III malocclusions and to find discriminant functions which would help to differentiate between favourable and unfavourable growers. The material consisted of cephalometric films of 115 Class III untreated patients (59 females and 56 males, with a mean age of 11.6 +/- 1.7 and 12.7 +/- 1.3 years, respectively) who were observed for a minimum period of 1 year. All subjects were Caucasian and none could achieve an edge to edge occlusion. Hierarchical cluster analysis was used to identify Class III subgroups. Discriminant function analysis (DFA) was first applied to the whole sample and later to each of the clusters produced. Good and poor growers were identified on the basis of the change in Wits measurements with projection on the maxillary/mandibular planes bisector. The cut-off point between good and bad growers was a Wits value of 2.5 mm which was the upper limit of the 95 per cent confidence interval of measurement reproducibility. Three clinically distinguishable clusters were produced, namely long, short and intermediate facial types. The discrimination percentage (80 per cent) achieved when the DFA was performed on the whole sample was satisfactory. However, when the analysis was used on each of the clusters separately, the equation successfully predicted a good or poor outcome in 92 per cent of cluster I, in 85 per cent of cluster II and in 100 per cent of cluster III.

Analysis of Variance↗

PubMed2000

Coarse root elongation rate estimates for interior Douglas-fir.

Accurate estimates of root growth rates are important for root system modeling, and the spread of root systems may be an important determinant of belowground site occupancy. Estimating root system growth rates is complicated because missing, discontinuous, and false annual growth rings make root cross sections difficult to age. These irregularities can occur even in roots of dominant conifers with rare or absent stem growth ring abnormalities. Incomplete rings were noted in the root growth rings of nine co-dominant interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) trees. Coarse root (> 1.0-cm diameter) elongation rates were estimated by fitting a geometric mean regression line to ring count and lateral distance data. In all nine roots examined, the geometric mean regression slope was well within the range of the 95% confidence interval for the ordinary least squares regression of lateral distance versus age, suggesting that measurement error may have been negligible. Coarse root elongation rates (which ranged from 2.8 to 15.3 cm year(-1) and averaged 7.4 cm year(-1)) in the interior Douglas-fir trees studied were much lower than those reported by others. This discrepancy may be a result of limited soil water availability, soil heterogeneity (both soil water content and soil texture were highly variable across short distances) and fragmentation of belowground growing space.

Journal Article↗

PubMedDate not supplied

The special extract ERr 731 of the roots of Rheum rhaponticum decreases anxiety and improves health state and general well-being in perimenopausal women.

OBJECTIVE: To investigate the efficacy of the special extract ERr 731 from the roots of Rheum rhaponticum compared with placebo on anxiety, health state, and general well-being in perimenopausal women. DESIGN: This study is a multicenter, prospective, randomized, double-blind, placebo-controlled clinical trial, in which 109 perimenopausal women with climacteric complaints and anxiety received either 1 enteric coated tablet of ERr 731 (n=54) or placebo (n=55) daily for 12 weeks. The Hamilton Anxiety Scale, the Menopause Rating Scale II, the Women's Health Questionnaire, and the Psychological General Well-Being Index were used to measure anxiety, health state, and subjective psychological well-being. RESULTS: The results demonstrate that ERr 731 is highly effective in reducing anxiety in perimenopausal women compared with placebo. After 12 weeks, the Hamilton Anxiety Scale total score decreased significantly with ERr 731 (from 27.5+/-6.8 to 9.4+/-4.2 points) compared with placebo (from 25.1+/-6.0 to 21.6+/-8.6 points). ERr 731 also reduced the Hamilton Anxiety Scale factor scores for somatic and psychic anxiety. After 12 weeks, a reduction in the severity of anxiety from "moderate" or "severe" to "slight" was observed in 33 of 39 ERr 731 women completing the double-blind phase, which correlated well with the reduction in number and severity of hot flushes. This was reflected by a high rate of ERr 731 women reporting a marked improvement in health state and general well-being. CONCLUSIONS: ERr 731 is an effective medication for women with menopause-related anxiety and improves their health state and general well-being.

Anxiety Disorders↗