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Query: UMLS:C0016382 (flushing)
 6,387 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cooling is accepted as a practical way of lowering cell metabolism in vein grafts during coronary by-pass surgery. We have previously shown that low temperature causes endothelial cells to become detached, both in in vitro and in vein graft. In this study we have looked at the effect of cold on the concentrations of intra- and extracellular electrolytes. Human endothelial cells were grown on titanium grids for electron microscopy. The cells were incubated for 30 min at 37 degrees, 20 degrees, and 4 degrees C with cell culture medium containing human serum, and at 20 degrees and 4 degrees C with heparinized sodium acetate solution with serum, frequently used for flushing and distending vein grafts. Freeze-dried cells were then subjected to elemental X-ray microanalysis. The ambient fluid was analysed by flame photometry. At 20 degrees and 4 degrees C, intracellular concentration of sodium increased, and potassium decreased, compared with controls (37 degrees C). The changes in sodium concentrations were aggravated when cell culture medium was replaced by heparinized sodium acetate. The intracellular chloride concentration did not change when cells were stored in cold cell culture medium. The extracellular concentration of potassium increased with increasing incubation time at 4 degrees C. The connection between these findings and cell detachment is discussed.
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PMID:Effect of cooling on the intracellular concentrations of Na+, K+ and Cl- in cultured human endothelial cells. 321 59

16 models of valves, currently in use in the U.K., have been tested long-term in the U.K. Shunt Evaluation Laboratory according to the protocol based on the new ISO 7197 standard. Valves tested were: Medtronic PS Medical: Delta Valve, Flow Control and Lumbo-Peritoneal Shunt, Heyer-Schulte Nero-Care: In-line, Low Profile and Pudenz Flushing Valve, Codman: Codman-Hakim Programmable, Hakim Precision, Accu-Flo, Holter, Uni-Shunt, and siphon-preventing device -- SiphonGuard, NMT: Orbis-Sigma Valve, Omni-Shunt and Hakim Valve, Sophysa: Sophy Programmable Valve, Radionics: Contour-Flex Valve. The majority of the valves had a non-physiologically low hydrodynamic resistance (with the exception of Orbis-Sigma, PS Lumbo-Peritoneal and Heyer-Schulte In-Line). This may result in overdrainage both related to posture and during nocturnal cerebral vasogenic waves. A long distal catheter increases the resistance of these valves by 100-200%. Drainage through valves without siphon-preventing mechanism is very sensitive to body posture. This may produce grossly negative intracranial pressure after implantation. A few shunts (Delta, Low Profile and Pudenz-Flushing with Anti-Siphon Devices) offer a reasonable resistance to negative outlet pressure, and hence potentially might prevent complications related to overdrainage. On the other hand, valves with siphon-preventing devices may be blocked by raised subcutaneous pressure (exception: SiphonGuard, but this device may block the drainage because of its faulty design). In most of the silicone-diaphragm valves, closing pressure varied and reached values lower than that specified by the manufacturer (exception: Heyer-Schulte Pudenz Flushing Valve). All programmable valves are susceptible to overdrainage in the upright body position. Programmed settings may be changed by external magnetic fields. Most shunts are very sensitive to the presence of small particles in the drained fluid. The behavior of a valve revealed during such testing is of immediate relevance to the surgeon and may not be adequately described in the manufacturer's product information. These results are also relevant to the assessment of shunt function in-vivo using an infusion test.
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PMID:Laboratory testing of hydrocephalus shunts -- conclusion of the U.K. Shunt evaluation programme. 1211 85

Leaf maturation in mountain birch (Betula pubescens ssp. czerepanovii) is characterized by rapid shifts in the types of dominant phenolics: from carbon-economic flavonoids aglycons in flushing leaves, via hydrolysable tannins and flavonoid glycosides, to carbon-rich proanthocyanidins (condensed tannins) in mature foliage. This shift accords with the suggested trade-offs between carbon allocation to plant defense and growth, but may also relate to the simultaneous decline in nutritive leaf traits, such as water, proteins and sugars, which potentially limit insect growth. To elucidate how birch leaf quality translates into insect growth, I introduce a simple model that takes into account defensive compounds but also acknowledges insect demand for nutritive compounds. The effects of defensive compounds on insect growth depend strongly on background variation in nutritive leaf traits: compensatory feeding on low nutritive diets increases the intake of defensive compounds, and the availability of growth-limiting nutritive compounds may modify the effects of defenses. The ratio of consumption to larval growth (both in dry mass) increases very rapidly with leaf maturation: from 2.9 to 9.8 over 2 weeks in June-July, and to 15 by August. High concentrations in mature birch leaves of "quantitative" defenses, such as proanthocyanidins (15-20% of dry mass), presumably prevent further consumption. If the same compounds had also protected half-grown leaves (which supported the same larval growth with only one third of the dry matter consumption of older leaves), the same intake of proanthocyanidins would have demanded improbably high concentrations (close to 50%) in young leaves. The model thus suggests an adaptive explanation for the high levels of "quantitative" defenses, such as proanthocyanidins, in low-nutritive but not in high-nutritive leaves because of the behavioral responses of insect feeding to leaf nutritive levels.
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PMID:Putting the insect into the birch-insect interaction. 1268 56

Changes in net carbon assimilation and water status were studied during leaf development in the deciduous, tropical species Brachystegia spiciformis Benth. In this upland savanna African tree, bud-burst and leaf development occur approximately two months before the rainy season. The newly formed leaves synthesize anthocyanin until the fully expanded leaves of the whole canopy are red. This foliage is referred to as "spring flush" foliage. Subsequently, the anthocyanins are metabolized and the pre-rain leaves become green. Carbon dioxide assimilation exhibited a bimodal diurnal pattern and was similar for pre-rain green leaves and fully expanded flushing leaves, although pre-rain green leaves showed a net uptake of carbon throughout the daylight period, whereas flushing leaves exhibited only brief periods of net photosynthesis in the morning and early afternoon. Measurements of leaf water potential and relative water content showed a diurnal pattern with considerable variation throughout the day. Leaf water potential and relative water content values decreased soon after sunrise reaching a minimum at a time corresponding to the afternoon peak in CO(2) assimilation. Stomatal conductance was closely related to transpiration rate in both flushing and pre-rain green leaves, although flushing leaves had lower stomatal conductances than pre-rain green leaves. Pre-rain green leaves exhibited a compensation irradiance of approximately 180 micro mol m(-2) s(-1), whereas flushing leaves had positive net photosynthesis only at PPFDs greater than 300 micro mol m(-2) s(-1). Rate of photosynthesis (expressed per leaf area or chlorophyll unit) increased as anthocyanin concentration decreased, although the photosynthetic rate continued to increase long after the leaf anthocyanins had been degraded to low, visually undetectable amounts. Post-rain green leaves had chlorophyll concentrations, transpiration rates and stomatal conductances similar to those of pre-rain green leaves; however, photosynthetic rates in post-rain leaves were more than three times higher. Thus, during the early stages of the spring flush, carbon asimilation rates of the flushing leaves were inversely related to leaf anthocyanin concentrations. In pre-rain green leaves, photosynthesis was limited by other non-stomatal factors.
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PMID:Changes in photosynthesis and water status of developing leaves of Brachystegia spiciformis Benth. 1496 98

The pool size of mobile, i.e. non-structural carbohydrates (NSC) in trees reflects the balance between net photosynthetic carbon uptake (source) and irreversible investments in structures or loss of carbon (sink). The seasonal variation of NSC concentration should reflect the sink/source relationship, provided all tissues from root to crown tops are considered. Using the Smithsonian canopy crane in Panama we studied NSC concentrations in a semi-deciduous tropical forest over 22 months. In the 9 most intensively studied species (out of the 17 investigated), we found higher NSC concentrations (starch, glucose, fructose, sucrose) across all species and organs in the dry season than in the wet season (NSC 7.2% vs 5.8% of dry matter in leaves, 8.8/6.0 in branches, 9.7/8.5 in stems, 8.3/6.4 in coarse and 3.9/2.2 in fine roots). Since this increase was due to starch only, we attribute this to drought-constrained growth (photosynthesis less affected by drought than sink activity). Species-specific phenological rhythms (leafing or fruiting) did not overturn these seasonal trends. Most of the stem volume (diameter at breast height around 40 cm) stores NSC. We present the first whole forest estimate of NSC pool size, assuming a 200 t ha(-1) forest biomass: 8% of this i.e. ca. 16 t ha(-1) is NSC, with ca. 13 t ha(-1) in stems and branches, ca. 0.5 and 2.8 t ha(-1) in leaves and roots. Starch alone (ca. 10.5 t ha(-1)) accounts for far more C than would be needed to replace the total leaf canopy without additional photosynthesis. NSC never passed through a period of significant depletion. Leaf flushing did not draw heavily upon NSC pools. Overall, the data imply a high carbon supply status of this forest and that growth during the dry season is not carbon limited. Rather, water shortage seems to limit carbon investment (new tissue formation) directly, leaving little leeway for a direct CO2 fertilization effects.
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PMID:Non-structural carbohydrate pools in a tropical forest. 1557 27

Various needle sizes (17- and 20-g) and aspiration pressures (25, 50, 75 and 100 mmHg) were used to aspirate a total of 5,827 ovarian follicles from bovine ovaries from a slaughterhouse source to assess the impact on the quantity and quality of recovered immature oocytes. The cumulus oocyte complexes (COC's) were graded according to the presence and consistency of cumulus cells surrounding the oocyte and the data analyzed using general linear models. Overall recovery rates and the recovery of oocytes considered viable for IVM/IVF procedures (Classes A, B and C) were both significantly higher using a 17-g needle than a 20-g needle (P < 0.01). As the vacuum pressure increased so did the recovery rate of the total number of oocytes, although the number of viable oocytes reached a maximum at a calculated vacuum pressure of 55 mmHg for the 17-g needle and 77 mmHg for the 20-g needle, with an increased incidence of denuded oocytes at higher vacuum pressures. In a second experiment conducted on 1, 473 follicles, no significant difference was found between 17-g double (flushing) and 17-g single lumen needles in the recovery rate of either the total number or number of viable oocytes when using a vacuum pressure of 50 mmHg.
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PMID:The collection of oocytes from bovine ovaries. 1672 47

We conducted experiments in laboratory microcosms to simulate input of stemflow nutrients and flushing of metabolites in the tree hole habitats of larval Ochlerotatus triseriatus (Say). In the first experiment, we simultaneously examined the effects of nutrient additions (nitrogen, phosphorus, glucose, or combination) and flushing (removal of one-half of water volume replaced by deionized water) on mosquito production. The combination of nutrients had the greatest positive effects on mosquito production, with nitrogen (N) likely accounting for most of the increase in adult emergence and adult mass. Dilution of the nutrient pool via simulated flushing reduced mosquito growth, suggesting that the primary effect of stemflow input was nutrient addition as opposed to dilution of any latent toxic metabolites. In a second experiment, N additions were crossed with larval presence or absence to examine effects on key microbial processes. N increased leaf decay rates, soluble carbohydrate concentrations, fungal biomass and leaf-associated carbohydrase activity, but it did not stimulate bacterial productivity. Leaf decay was enhanced and bacterial production on leaves and in the water column was depressed in the presence of larvae. We conclude that the inputs of soluble N stimulated fungal growth, which made more fungal biomass available because of both its absolute increase and via the softening of the leaf particulate matter that could allow direct ingestion by larvae.
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PMID:Indirect effects of soluble nitrogen on growth of Ochlerotatus triseriatus larvae in container habitats. 1689 24

Dry forests are common, although highly threatened in the Neotropics. Their ecological processes are mostly influenced by rainfall pattern, hence their cycles exhibit contrasting phases. We studied the phenology of canopy trees in a primary dry forest in Western Brazil in the foothills of the Urucum mountain chain, in order to improve our knowledge on the functioning of these poorly-known forests. Leaf shedding started in the early dry season and was massive in the latter part of this period. Most leaf loss occurred in dry hills, while wet valleys remained evergreen. Anemochorich and autochorich species predominated in dry hills, presumably due to their tolerance to dry conditions and enhanced exposition to winds, which favour diaspores removal and dispersal. Conversely, zoochorich species dominated the wet valleys. Flowering was intense in the late dry season, the driest period of the year, while fruiting was massive just after the onset of rains, as well as flushing. Therefore, most flowering was unrelated to wet conditions, although such an abiotic factor, potentially, triggered the major fruiting episode, widely comprised by zoochorich species. Anemochorich and autochorich species flowered and fruited in the course of the long dry season. The contrasting environmental conditions present in the hills and valleys determine the arrangement of a mosaic in which patches of zoochorich and evergreen trees alternate with patches of non zoochorich and highly deciduous species. Consequently, species with such syndromes exhibited marked flowering and fruiting patterns, accordingly to the pronounced seasonality.
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PMID:Canopy phenology of a dry forest in western Brazil. 1809 42

Seasonal tropical forests exhibit a great diversity of leaf exchange patterns. Within these forests variation in the timing and intensity of leaf exchange may occur within and among individual trees and species, as well as from year to year. Understanding what generates this diversity of phenological behaviour requires a mechanistic model that incorporates rate-limiting physiological conditions, environmental cues, and their interactions. In this study we examined long-term patterns of leaf flushing for a large proportion of the hundreds of tree species that co-occur in a seasonal tropical forest community in western Thailand. We used the data to examine community-wide variation in deciduousness and tested competing hypotheses regarding the timing and triggers of leaf flushing in seasonal tropical forests. We developed metrics to quantify the nature of deciduousness (its magnitude, timing and duration) and its variability among survey years and across a range of taxonomic levels. Tree species varied widely in the magnitude, duration, and variability of leaf loss within species and across years. The magnitude of deciduousness ranged from complete crown loss to no crown loss. Among species that lost most of their crown, the duration of deciduousness ranged from 2 to 21 weeks. The duration of deciduousness in the majority of species was considerably shorter than in neotropical forests with similar rainfall periodicity. While the timing of leaf flushing varied among species, most ( approximately 70%) flushed during the dry season. Leaf flushing was associated with changes in photoperiod in some species and the timing of rainfall in other species. However, more than a third of species showed no clear association with either photoperiod or rainfall, despite the considerable length and depth of the dataset. Further progress in resolving the underlying internal and external mechanisms controlling leaf exchange will require targeting these species for detailed physiological and microclimatic studies.
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PMID:Deciduousness in a seasonal tropical forest in western Thailand: interannual and intraspecific variation in timing, duration and environmental cues. 1818 4

In tropical dry forests most plants are deciduous during the dry season and flush leaves with the onset of the rains. In Costa Rica, the only species displaying the opposite pattern is Bonellia nervosa. To determine if seasonal changes in light availability are associated with the leaf and reproductive phenology of this species, we monitored leaf production, survival, and life span, as well as flower and fruit production from April 2000 to October 2001 in Santa Rosa National Park. Leaf flushing and flower bud production took place shortly after the autumnal equinox when day length starts to decrease. Leaves began expansion at the end of the wet season, and plants reached 70 % of their maximum leaf area at the beginning of the dry season, maintaining their foliage throughout the entire dry period. Leaf shedding occurred gradually during the first three months of the wet season. Leaf flushing and shedding showed high synchrony, with leaf numbers being related to light availability. Maximum leaf production coincided with peaks in radiation during the middle of the dry season. Decreasing day length induces highly synchronous flower bud emergence in dry forest species, but this is the first study indicating induction of leaf flushing by declining day length.
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PMID:Do seasonal changes in light availability influence the inverse leafing phenology of the neotropical dry forest understory shrub Bonellia nervosa (Theophrastaceae)? 1862 41


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