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At least 109 records · Page 6Linked to original sources
PubMed2001

Dynamics of PAH deposition, cycling and storage in a mixed-deciduous (Quercus-Fraxinus) woodland ecosystem.

Estimates of standing biomass and fluxes of biomass in a mixed-deciduous woodland were derived, and used with results for concentrations of seven polycyclic aromatic hydrocarbons (PAHs) in different compartments of the woodland system to quantitatively assess some of the key fluxes and burdens of PAHs in this complex system. We quantified PAH burdens in air, in leaves of three deciduous tree species, in leaf litter and in soil, and uptake of PAHs by the tree leaves; PAH fluxes in litterfall, and deposition to the litter layer on the woodland floor during winter were calculated from these data. Air burdens exhibited marked seasonal variations for all compounds, with lowest values in summer when combustion-related emissions were low. Leaves did not accumulate large burdens of PAHs while on the trees and consequently, litterfall-associated fluxes of PAHs were small, representing only a fraction of the burdens in the litter layer to which they were deposited. Higher PAH burdens in air in winter, combined with the organic-matter-rich nature of the litter layer, are thought to be responsible for fluxes of PAHs to the litter layer in winter being 20-170 times the peak litterfall fluxes. The soil compartment was calculated to contain 25 years' worth of deposition of benzo[ghi]perylene, the most recalcitrant PAH in this study. Storage quotients for fluoranthene, pyrene, benzo[k]fluoranthene and benzo[a]pyrene burdens in soil represented 7-10 years' worth of deposition, while fluorene and phenanthrene storage in soil approached unity with inputs (1 and 3 years' worth of deposition, respectively). The relative importance of storage and loss processes was therefore closely related to the physico-chemical properties of the PAH, and is discussed in relation to the cycling of carbon in the woodland.

Carbon↗
PubMed2001

Assessment of genetic structure within and among Bulgarian populations of the common ash (Fraxinus excelsior L.).

We analysed genetic variation within and between populations of the common ash from Bulgaria in order to extract biological information useful in the context of conservation management of eastern European genetic resources of noble hardwood species. A total of 321 trees from three regions of Bulgaria were typed at six highly polymorphic microsatellite loci. Analysis of within-population inbreeding suggests an upper boundary value of 2.7% for the selfing rate. Significant spatial genetic structure consistent with models of isolation by distance was detected within four out of 10 populations as well as among populations. Estimates of neighbourhood size in the range 38-126 individual trees were obtained based on spatial genetic structure analyses at either the intrapopulation or interpopulation level. Differentiation among populations explained only about 8.7% of total genetic diversity. These results are discussed in comparison with data from social broad-leaved species such as oak and beech.

Alleles↗
PubMed1966

On the fine structure of the cambium of Fraxinus americana L.

The fine structure of ash cambium was studied after glutaraldehyde-osmium tetroxide fixation. The fusiform and ray initials are essentially alike, and both have the basic complement of organelles and membranes typical of parenchyma cells. The varied behavior of the two types of initials and the role of cambium in oriented production of the xylem and phloem are still unexplained phenomena. Actively growing cambial cells are highly vacuolate. They are rich in endoplasmic reticulum of the rough cisternal form, ribosomes, dictyosomes, and coated vesicles. Microtubules are present in the peripheral cytoplasm. The plasmalemma appears to be continuous with the endoplasmic reticulum and produces coated vesicles as well as micropinocytotic vesicles with smooth surfaces. The plastids have varying amounts of an intralamellar inclusion which may be a lipoprotein. The quiescent cambium is deficient in rough ER and coated vesicles and has certain structures which may be condensed proteins.

Cell Membrane↗
PubMed1997

Occupational asthma and rhinitis caused by ash (Fraxinus excelsior) wood dust.

An 18-year-old man who worked in a furniture factory reported rhinitis and asthma when he was exposed to ash wood dust. Monitoring of the patient's peak expiratory flow rate (PEFR) when off work and at work showed increased variations of PEFR at work. Basal PC20 methacholine was 1.41 mg/ml. A bronchial provocation test (BPT) with a 1:1000 w/v ash wood dust extract induced a dual asthmatic response with a 7.5-fold increase of nonspecific bronchial responsiveness. Intradermal testing with ash wood extract elicited a positive immediate response. IgE antibodies against ash wood were found in the patient's serum with a RAST value of 0.57 PRU/ ml. Similar skin tests, BPT, and RAST with ash wood dust performed in control patients were all negative. All the studies performed suggest that our patient had occupational rhinitis and asthma caused by exposure to ash wood dust in which a type I immunologic mechanism was implicated.

Adolescent↗
PubMed1993

[Casparus Fraxinus at the University of Padua].

This article, as addition to the previous ones, analyses the 16th century Hungarian physician's, Gáspár Korös' studies at the University Padoua. Giving a detailed description of the contemporary Padouan-Hungarian cultural connections, the author attempts to reconstruate the effects and circumstances this time Korös was influenced by. The author, while listing the professors, whose teaching proved to be determinative for the young Hungarian physician, refutes some mistakes based on the earlier medical historical literature. In its second part, the article focuses on the importance of the personal connections in the carreer of Korösi, who after his return to Hungary played an important role in the medical history of the country.

Education, Medical↗
PubMed1989

Occupational asthma caused by exposure to ash wood dust (Fraxinus americana).

A 63 year old man reported rhinitis and asthma, which occurred only at work where he was exposed to ash wood dust. Monitoring of peak expiratory flow rates (PEFR) and bronchial responsiveness to histamine when off work and at work showed increased variation of PEFR at work but no significant changes in nonspecific bronchial responsiveness assessed by the provocation concentration producing a 20% fall in FEV1 (PC20). Specific inhalation challenges were carried out in a special challenge room with ash wood dust. During the exposure for only 3 minutes, the mean concentration of particles was 3 mg-m3 and about 50% of particles had a diameter less than 10 mu. An immediate bronchospastic reaction was documented. Antibodies to a human serum albumin (HSA) ash wood conjugate were not significantly increased.

Asthma↗