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At least 289 records · Page 16Linked to original sources
PubMed1994

Characterization of a Rickettsia rickettsii DNA fragment analogous to the fir A-ORF17-lpxA region of Escherichia coli.

The firA and lpxA genes, as well as an ORF coding for a putative 16-kDa protein of unknown function, have been identified and characterized in the obligate intracellular bacterium. Rickettsia rickettsii. This is the first description of these genes, which code for enzymes involved in the biosynthesis of lipid A, in a species outside of the Enterobacteriaceae. The deduced amino acid (aa) sequences of FirA, ORF16 and LpxA of R. rickettsii, when compared to their Escherichia coli analogs, exhibited 35, 44 and 41% aa identity, respectively. In addition, the order of genes in R. rickettsii, firA-ORF16-lpxA, was identical to that found in E. coli; however, the spacing between the rickettsial genes was greater. Interestingly, the R. rickettsii FirA and LpxA deduced proteins retain an unusual hexapeptide repeat pattern found in E. coli and Salmonella typhimurium FirA/Ssc and E. coli LpxA, as well as other acyltransferases, providing additional support for the importance of this structure.

Acyltransferases↗
PubMed2004

The TL analysis methods used to determine absorbed gamma doses in vivo for the BNCT patients treated at FiR 1.

The gamma dose determination using thermoluminescent (TL) dosimeters in mixed neutron-gamma fields, such as in boron neutron capture therapy (BNCT), is difficult due to the thermal neutron sensitivity of the detectors; especially when equipment capable of glow curve analysis is not available. The two TL analysis methods used previously in Finnish BNCT to correct the measured TL signal to obtain absorbed gamma dose in vivo were studied and compared, and an enhanced method was introduced. The three TL methods were found surprisingly consistent despite, e.g. the rough estimate made in the first method.

Boron Neutron Capture Therapy↗
PubMed2003

A coded approach to system identification using a modified Golay FIR filter.

Several techniques are currently in use for system identification, each having its own level of performance. In this paper we present a coded interrogation approach for statistical system identification; it is based around a modified Golay sequence applied to an adaptive finite impulse response (AFIR) filter system. We show that this technique circumvents some of the shortfalls associated with other comparative approaches. The theory of the proposed technique is developed, and the operating principle of a prototype model to verify it is described. Analysis of the results obtained from experiments, performed on a simple first-order linear time invariant (LTI) system, gave an average deviation of +/- 2.94% from the ideal response.

Algorithms↗
PubMed2006

Gene expression profiles of different breast cancer cells compared with their responsiveness to fermented mistletoe (Viscum album L.) extracts Iscador from oak (Quercus), pine (Pinus), white fir (Abies) and apple tree (Malus) in vitro.

Cytotoxicity assays in vitro (MTT test) showed that the different breast cancer cell lines Kpl-1, MCF-7 and Mfm-223 respond differently to the mistletoe (Viscum album L.) preparations Iscador. Quercus (Qu), Abies (A), Malus (M) and Pinus (P). In order to determine the differences in the responsiveness of the cells more exactly, the gene expression profiles were determined by cells, which were treated with Mistletoe extracts, compared with untreated control cells. Such differences can be analysed in more detail by looking at the gene expression using Human Whole Genome microarray chips (41,000 genes). The results of the transcriptome analyses suggested that Iscador preparations influenced the overregulation of genes regarding immune defense, stress response, apoptosis and cell-cell adhesion pathways. Within the Mfm-223-Zellen was the Genexpression in MCF-7 and Kpl-1. The MCF-7 cells were affected on the genes which are involved in cell-cell contacts whereas Kpl-1 responded to the mistletoe extracts by changing the mRNA levels of the immune and stress response pathways. Concerning the effects of the mistletoe extract, we conclude that Iscador Qu and M have a greater influence on the immune defense and stress response genes whereas Iscador A tends to affect the cell-cell adhesion and cytoskeleton pathways. In summary, cDNA microarray analyses give us information on whether a cancer cell is sensitive to mistletoe extracts in relation to how many genes are significantly overrepresented after mistletoe treatment, and whether a particular mistletoe extract is more effective on a specific cancer cell than the other preparation.

Abies↗
PubMedDate not supplied

Health hazards to timber and forestry workers from the Douglas fir tussock moth.

A heavy infestation of the tussock moth caterpillar (Orgyia pseudotsugata McDonnough) in forested areas of Oregon was associated with itching of the skin and eyes, nasal discharge, cough, and, at times, respiratory difficulty, Personal interviews and inspection of forty-one occupationally exposed persons were supplemented by a questionnaire administered to 428 individuals, composing three groups at various degrees of risk and a control group. There was a cause and effect relationship between the adverse symptoms and the exposure to tussock moth larvae. The specific etiologic agent was not identified, but it was felt that the secretion, hairs, or other substances in the larvae or cocoons of the moth acted as a potent allergenic substance and, for some persons, was also a primary skin irritant.

Animals↗
PubMed2003

Branch junctions and the flow of water through xylem in Douglas-fir and ponderosa pine stems.

Water flowing through the xylem from the roots to the leaves of most plants must pass through junctions where branches have developed from the main stem. These junctions have been studied as both flow constrictions and components of a hydraulic segmentation mechanism to protect the main axes of the plant. The hydraulic nature of the branch junction also affects the degree to which branches interact and can respond to changes in flow to other branches. The junctions from shoots of two conifer species were studied, with particular emphasis on the coupling between the downstream branches. Flow was observed qualitatively by forcing stain through the junctions and the resulting patterns showed that flow into a branch was confined to just part of the subtending xylem until a considerable distance below the junction. Junctions were studied quantitatively by measuring flow rates in a branch before and after flow was stopped in an adjacent branch and by measuring the hydraulic resistance of the components of the junction. Following flow stoppage in the adjacent branch, flow into the remaining branch increased, but considerably less than predicted based on a simple resistance analogue for the branch junction that assumes the two branches are fully coupled. The branches downstream from a junction, therefore, appear to be limited in their interconnectedness and hence in their ability to interact.

Biological Transport↗
PubMed1995

Carbon isotope variation in Douglas-fir foliage: improving the delta(13)C-climate relationship.

The natural abundance of stable carbon isotopes in the annual rings of forest trees is used as a tracer of environmental changes such as climate and atmospheric pollution. Although tree-ring delta(13)C varies by about 2 per thousand from year to year, variability within the foliage can be as high as 6 per thousand. Recent studies have shown that branch length affects stomatal response, which influences the integrated foliar delta(13)C signal. To improve the ability of delta(13)C to predict climate differences, we examined the relationship between branch length and foliar delta(13)C in Pseudotsuga menziesii (Mirb.) Franco from four sites across a steep climate gradient in Oregon. The transect spanned the boundary between the ranges of the coastal variety, P. menziesii var. menziesii (three sites), and the Rocky Mountain variety, P. menziesii var. glauca (one site). At the most maritime site, branch length explained 76% of within-site variation of 5 per thousand, whereas at the harshest site, branch length accounted for only 15% of this variation. We considered the possibility that cavitation in the water-conducting xylem obscures the branch length effect in the harsher climates. Cavitation, as measured by dye perfusion, was most extensive at sites where the branch length effect in the coastal variety was weakest. Trees at the site with the most substantial cavitation displayed seasonal xylem refilling. Branch length standardization significantly improved the relationship between delta(13)C and climate. With standardization to constant length, delta(13)C values were significantly related to the degree that climatic variables, as modeled with a forest growth simulation model, constrain transpiration (R(2) = 0.69, P < 0.0001). Without standardization, the R(2) was 0.27. We conclude that sampling standard length branches or tree rings from trees of similar shape and size is desirable when seeking correlations between isotopic composition and climate.

Journal Article↗
PubMed1995

In vitro regeneration of Pacific silver fir (Abies amabilis) plantlets and histological analysis of shoot formation.

A protocol is described for the in vitro propagation of Abies amabilis (Dougl.) Forbes. Over 60% of the cotyledonary explants from 5-day-old cotyledons formed shoots when cultured for 7 days on Schenk and Hildebrandt's (SH) medium containing 10 micro M N(6)-benzyladenine (BA) followed by another 7 days on SH medium containing 10 micro M each of BA and zeatin. Shoot multiplication was unsuccessful. Seventeen percent rooting was obtained after pulsing for 4 h in 1 mM indole-3-butyric acid and planting pulsed shoots in 1/1 (v/v) perlite/vermiculite. Cell clusters (promeristemoids) of five to seven cells were observed on the cotyledonary explants after 7 days of culture in the presence of cytokinin. These cells developed further into meristematic domes and apical meristems. In the absence of cytokinin, stomata and resin canals reached maturity, whereas cells within the cortex became vacuolated and developed into palisade and spongy mesophyll.

Journal Article↗
PubMed2000

Effects of stand composition and thinning in mixed-species forests: a modeling approach applied to Douglas-fir and beech.

Models estimating growth and yield of forest stands provide important tools for forest management. Pure stands have been modeled extensively and successfully for decades; however, relatively few models for mixed-species stands have been developed. A spatially explicit, mechanistic model (COMMIX) is presented that simulates growth of mixed-species forest stands, and takes account of the effects of management on stand dynamics. Previously, it was shown that COMMIX satisfactorily reproduced the development of monospecific stands. In the present study, the model was used to simulate growth and yield in mixed stands differing in the proportions of species present. The concept of a "replacement series" was used to compare productivities of the mixed stands. The model was also used to analyze effects of thinning regimes and stand composition on productivity. Model simulations indicate that productivity of a mixed stand will generally be intermediate between the productivities of monospecific stands of the contributing species. However, stand composition, and especially thinning regime, will strongly affect stand productivity. The simulations are discussed with reference to the effects of resource partitioning, canopy stratification, complementarity, spatial pattern, crown dynamics, and phenology on the growth and yield of mixed stands. The study highlights the value of using mechanistic approaches to predict mixed stand development in relation to management regime.

Journal Article↗
PubMed2002

Canopy and hydraulic conductance in young, mature and old Douglas-fir trees.

We tested for reductions in water transport with increasing tree size, a key component in determining whether gas exchange and growth are hydraulically limited in tall trees. During the summers of 1998 and 1999, we measured water transport with Granier-type, constant-heat sap flow probes, vapor pressure deficit, and leaf and soil water potentials in overstory Pseudotsuga menziesii (Mirb.) Franco trees in three stands differing in size and age (15, 32 and 60 m in height and about 20, 40 and 450 years in age, respectively) in a P. menziesii-dominated forest in the Pacific Northwest, USA. A total of 24 trees were equipped with sap flow sensors--six 60-m trees, nine 32-m trees and nine 15-m trees. Based on the sap flow measurements and leaf area information estimated from leaf area-sapwood area relationships, we estimated crown-averaged stomatal conductance (GS) and leaf-specific hydraulic conductance (KL). We tested the hypothesis that GS and KL vary inversely with tree height (15 > 32 > 60 m). Analysis of variance of GS ranked as 15 = 60 > 32 m during the early summer and 15 > 60 > 32 m during late season drought. Over the growing season, mean daily GS (+/- SE) was 29.2 +/- 4.4, 24.0 +/- 6.8 and 17.7 +/- 7.2 mmol m-2 s-1 for the 15-, 60- and 32-m trees, respectively. The value of K(L) differed among tree heights only during late season drought and ranked 15 > 32 = 60 m. A hydraulic mass balance suggests that greater sapwood conductivity in 60-m trees compared with 32- and 15-m trees is a likely cause for the departure of the above rankings from those predicted by height and leaf-to-sapwood area ratio.

Circadian Rhythm↗