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Biomedical subjects

A Granier

Publications and source records attributed to A Granier.

11 recordsLinked to original sources
PubMed2001

Mechanisms of xylem recovery from winter embolism in Fagus sylvatica.

Hydraulic conductivity in the terminal branches of mature beech trees (Fagus sylvatica L.) decreased progressively during winter and recovered in the spring. The objective of this study was to determine the mechanisms involved in recovery. Two periods of recovery were identified. The first recovery of hydraulic conductivity occurred early in the spring, before bud break, and was correlated with the occurrence of positive xylem pressure at the base of the tree trunk. Active refilling of the embolized vessels caused the recovery. The second recovery of hydraulic conductivity occurred after bud break and was correlated with the onset of cambial activity. Formation of new functional vessels, leading to an increase in xylem diameter, was largely responsible for the increase in xylem conductivity. The two mechanisms were complementary: active refilling of embolized vessels occurred mostly in the root and the trunk, whereas formation of new functional vessels occurred mainly in young terminal shoots.

Plant Diseases↗
PubMed2001

Seasonal dynamics of soil carbon dioxide efflux and simulated rhizosphere respiration in a beech forest.

Respiration of the rhizosphere in a beech (Fagus sylvatica L.) forest was calculated by subtracting microbial respiration associated with organic matter decomposition from daily mean soil CO2 efflux. We used a semi-mechanistic soil organic matter model to simulate microbial respiration, which was validated against "no roots" data from trenched subplots. Rhizosphere respiration exhibited pronounced seasonal variation from 0.2 g C m(-2) day(-1) in January to 2.3 g C m(-2) day(-1) in July. Rhizosphere respiration accounted for 30 to 60% of total soil CO2 efflux, with an annual mean of 52%. The high Q10 (3.9) for in situ rhizosphere respiration was ascribed to the confounding effects of temperature and changes in root biomass and root and shoot activities. When data were normalized to the same soil temperature based on a physiologically relevant Q10 value of 2.2, the lowest values of temperature-normalized rhizosphere respiration were observed from January to March, whereas the highest value was observed in early July when fine root growth is thought to be maximal.

Carbon Dioxide↗
PubMed2000

Respiration as the main determinant of carbon balance in European forests.

Carbon exchange between the terrestrial biosphere and the atmosphere is one of the key processes that need to be assessed in the context of the Kyoto Protocol. Several studies suggest that the terrestrial biosphere is gaining carbon, but these estimates are obtained primarily by indirect methods, and the factors that control terrestrial carbon exchange, its magnitude and primary locations, are under debate. Here we present data of net ecosystem carbon exchange, collected between 1996 and 1998 from 15 European forests, which confirm that many European forest ecosystems act as carbon sinks. The annual carbon balances range from an uptake of 6.6 tonnes of carbon per hectare per year to a release of nearly 1 t C ha(-1) yr(-1), with a large variability between forests. The data show a significant increase of carbon uptake with decreasing latitude, whereas the gross primary production seems to be largely independent of latitude. Our observations indicate that, in general, ecosystem respiration determines net ecosystem carbon exchange. Also, for an accurate assessment of the carbon balance in a particular forest ecosystem, remote sensing of the normalized difference vegetation index or estimates based on forest inventories may not be sufficient.

Atmosphere↗
PubMed1989

[Extracorporeal lithotripsy in the treatment of biliary calculi].

The authors present their experience from February 1988 with biliary lithotripsy in 125 patients. They review the protocol inclusion criteria and the various forms of complementary medical treatment. From this group, 30% of the patients underwent cholecystectomy, 45% received medical treatment and only 25% did not eventually require complementary medical therapy.

Cholelithiasis↗
PubMed1982

[Puncture biopsy in the diagnosis of papillary epitheliomas of the thyroid].

In this study of the cytological appearances of papillary adenocarcinoma of the thyroid after fine needle aspiration biopsy, the authors have brought together 60 examinations of thyroid nodules and 10 indicant ganglial metastases. They isolate three significant aspects. type I (25 cases) is notable for the dense cellular desquamation in papillary clusters with angular contours, numerous calcospherites and, above all, the presence of intranucleaur pseudo-inclusion bodies (PI) which are clearly visible after coloring with May Grunwald stain. Type II (17 cases) was mainly observed in cystic lesions (8 cases) and metastatic ganglia (6 cases). It shows thick clusters of necrotic cells, few PI, barely visible against a background preparation of lysated hemates, polynuclear cells and macrophages. Type III (19 cases) consists of layers of cells poor in cytonuclear anomalies. The presence of PI is both a prerequisite and sufficent arounds for a diagnosis of papillary carcinoma of the thyroid, which will always be confirmed by subsequent histopathological examinations. The absence of PI leads to a false negative result. Better knowledge of cytological aspects specific to papillary tumors of the thyroid improves the quality of the diagnosis, not in terms of the percentage of carcinomas identified, which rises from 75.6 to 77% at a second reading, but in the specification of the papillary type, which rises from 38.5 to 64.2%. In the absence of PI and cytonuclear anomalies, non-identification of the carcinoma (22.8%) results from uninterpretable smears (5.7%) and false negatives (17.1%). There were no false positives. Cytological examination after fine needle aspiration biopsy should be included in the preoperative examinations of all thyroid nodules, as well as in the exploration of cervical ganglia likely to host an indicant or delayed metastasis.

Biopsy, Needle↗
PubMed1982

Estimation of coronary reserve in left anterior descending and circumflex coronary arteries by regional thermodilution technique.

The present study was attempted to determine whether a reduction in regional venous maximal coronary flow can indicate the presence of significant coronary stenosis. The great cardiac vein flow and the coronary sinus outflow were measured simultaneously in 8 open-chest dogs by a continuous thermodilution technique using a triple thermister catheter or two separate thermister catheters. The left anterior descending and circumflex coronary inflows were recorded using electromagnetic flow probes. Successive 70% coronary arterial stenosis maximal coronary flow and coronary reserve decreased significantly in the great cardiac vein and the coronary sinus. Significant correlations were found between the flows in the left anterior descending artery and in the great cardiac vein (r = 0.81) and between those in the circumflex artery and in the coronary sinus minus the great cardiac vein (r = 0.79) throughout the periods of preocclusion, occlusion and reactive hyperemic response. There were no significant changes in heart rate and hemodynamics. Using continuous thermodilution techniques, the inflows of the left anterior descending and the circumflex coronary arteries at a stenosis greater than 70% could be estimated from the changes in regional venous outflows.

Animals↗