Correlation between the ability of tumor cells to resist humoral immune attack and their ability to synthesize lipid.

Agents that increase (certain metabolic inhibitors, chemotherapeutic agents, and x-irradiation), decrease (hormones), or have no effect (hyperthermia) on the susceptibility of line-1 and line-10 guinea pig hepatoma cells to humoral immune attack were studied for their effects on the ability of these tumor cells to synthesize macromolecules. A correlation was found between the drug-induced increase in sensitivity of these cells to antibody-C mediated killing and the loss of their ability to incorporate fatty acids into complex cellular lipids. Similarly, the hormone-induced increase in resistance of the cells to killing was accompanied by an enhancement in complex lipid synthesis by these cells was also observed after the cells were exposed to physical means of insult (x-irradiation or hyperthermia). No correlation was found between the sensitivity of the cells to antibody-C mediated killing and their ability to synthesize DNA, RNA, protein, or complex carbohydrate, or their capacity for de novo lipid synthesis as measured by incorporation of acetate and glycerol into cellular macromolecules. The assembly of free fatty acids into complex lipid moieties is therefore proposed to be of fundamental importance for the ability of the tumor cells to resist humoral immune killing.     

Ecological implications of plants' ability to tell the time

The circadian clock (the endogenous mechanism that anticipates diurnal cycles) acts as a central coordinator of plant activity. At the molecular and organism level, it regulates key traits for plant fitness, including seed germination, gas exchange, growth and flowering, among others. In this article, we explore current evidence on the effect of the clock for the scales of interest to ecologists. We begin by synthesizing available knowledge on the effect of the clock on biosphere–atmosphere interactions and observe that, at least in the systems where it has been tested, the clock regulates gas exchange from the leaf to the ecosystem level, and we discuss its implications for estimates of the carbon balance. Then, we analyse whether incorporating the action of the clock may help in elucidating the effects of climate change on plant distributions. Circadian rhythms are involved in regulating the range of temperatures a species can survive and affects plant interactions. Finally, we review the involvement of the clock in key phenological events, such as flowering time and seed germination. Because the clock may act as a common mechanism affecting many of the diverse branches of ecology, our ultimate goal is to stimulate further research into this pressing, yet unexplored, topic.     

Acute hyperglycemia alters the ability of the normal beta-cell to sense and respond to glucose

Impaired glucose tolerance (IGT) and non-insulin-dependent diabetes mellitus (NIDDM) are associated with an impaired ability of the beta-cell to sense and respond to small changes in plasma glucose. The aim of this study was to establish whether acute hyperglycemia per se plays a role in inducing this defect in beta-cell response. Seven healthy volunteers with no family history of NIDDM were studied on two occasions during a 12-h oscillatory glucose infusion with a periodicity of 144 min. Once, low-dose glucose was infused at a mean rate of 6 mg x kg(-1) x min(-1) and amplitude 33% above and below the mean rate, and, once, high-dose glucose was infused at 12 mg x kg(-1) x min(-1) and amplitude 16% above and below the mean rate. Mean glucose levels were significantly higher during the high-dose compared with the low-dose glucose infusion [9.5 +/- 0.8 vs. 6.8 +/- 0.2 mM (P < 0.01)], resulting in increased mean insulin secretion rates [ISRs; 469.1 +/- 43.8 vs. 268.4 +/- 29 pmol/min (P < 0.001)] and mean insulin levels [213.6 +/- 46 vs. 67.9 +/- 10.9 pmol/l (P < 0.008)]. Spectral analysis evaluates the regularity of oscillations in glucose, insulin secretion, and insulin at a predetermined frequency. Spectral power for glucose, ISR, and insulin was reduced during the high-dose glucose infusion [11.8 +/- 1.4 to 7.0 +/- 1.6 (P < 0.02), 7.6 +/- 1.5 to 3.2 +/- 0.5 (P < 0.04), and 10.5 +/- 1.6 to 4.6 +/- 0.7 (P < 0.01), respectively]. In conclusion, short-term infusion of high-dose glucose to obtain glucose levels similar to those previously seen in IGT subjects results in reduced spectral power for glucose, ISR, and insulin. The reduction in spectral power previously observed for ISR in IGT or NIDDM subjects may be due partly to hyperglycemia.     

Thrombomodulin blocks the ability of thrombin to activate platelets

When thrombin is complexed to the endothelial cell surface receptor thrombomodulin, it loses its procoagulant activities in that it no longer clots fibrinogen or activates factor V. Studies were initiated to determine if complex formation also blocks thrombin's other major procoagulant function, the activation of platelets. When bound to thrombomodulin, thrombin no longer induces platelets to either aggregate or release [14C] serotonin. Binding studies using 125I-labeled thrombin or diisopropyl phosphorothrombin indicate that the complex does not bind to the platelet. When thrombomodulin is added after thrombin has bound to the platelets, the thrombin rapidly redistributes onto the thrombomodulin. These data suggest that in addition to its other anticoagulant effects, thrombomodulin may also act to inhibit and/or reverse platelet activation by thrombin.     

Exposure to salt and organic acids increases the ability of Listeria monocytogenes to invade Caco-2 cells but decreases its ability to survive gastric stress

The effects of environmental stress exposure on Listeria monocytogenes growth and virulence-associated characteristics were investigated. Specifically, we measured the effects of temperature (7 or 37 degrees C), pH (5.5 or 7.4), the presence of salt and organic acids (375 mM NaCl, 8.45 mM sodium diacetate [SD], 275 mM sodium lactate [SL], or a combination of NaCl, SD, and SL), and deletion of sigB, which encodes a key stress response regulator, on the ability of L. monocytogenes to grow, invade Caco-2 cells, and survive exposure to synthetic gastric fluid (pH 2.5 or 4.5). Our results indicate that (i) L. monocytogenes log-phase generation times and maximum cell numbers are not dependent on the alternative sigma factor sigmaB in the presence of NaCl and organic acids at concentrations typically found in foods; (ii) growth inhibition of L. monocytogenes through the addition of organic acids is pH dependent; (iii) the ability of L. monocytogenes to invade Caco-2 cells is affected by growth phase, temperature, and the presence of salt and organic acids, with the highest relative invasion capabilities observed for cells grown with SL or NaCl at 37 degrees C and pH 7.4; (iv) growth of L. monocytogenes in the presence of NaCl, SD, or SL reduces its ability to survive exposure to gastric fluid; and (v) exposure of L. monocytogenes to gastric fluid reduces the enhanced invasiveness caused by growth in the presence of NaCl or SL. These findings suggest that virulence-associated characteristics that determine the L. monocytogenes infectious dose are likely to be affected by food-specific properties (e.g., pH or the presence of salt or organic acid).     

Ontogeny of B-lymphocyte function: XII. Evidence that the ability to generate memory cells precedes the ability to produce antibody-secreting cells

Using a cell transfer system it was shown that lymphoid cells of B.C-9 mice mature to be able to generate a primary response of high magnitude and high affinity to dinitrophenylated γ-globulin at about 4 weeks of age. Irradiated mice reconstituted with lymphoid cells from B.C-9 or C57BL/6 donors younger than 4 weeks of age fail to produce high-affinity plaque-forming cells and their serum antibody responses were of low magnitude. Nevertheless such recipients give adult-like, high-affinity, high-magnitude secondary responses when assayed at both the plaque-forming cell and serum antibody levels. The antibody produced by the reconstituted mice, in both the primary and secondary responses, was shown to be of donor cell origin in transfers between allotype congenic pairs. Thus, naive, immature lymphoid cells, although not capable of giving rise to high-affinity antibody-secreting cells in a primary response, are capable of giving rise to high-affinity memory B cells which in turn can give an adult-like, high-affinity secondary response following boosting.     

Habitat stability affects dispersal and the ability to track climate change

Habitat persistence should influence dispersal ability, selecting for stronger dispersal in habitats of lower temporal stability. As standing (lentic) freshwater habitats are on average less persistent over time than running (lotic) habitats, lentic species should show higher dispersal abilities than lotic species. Assuming that climate is an important determinant of species distributions, we hypothesize that lentic species should have distributions that are closer to equilibrium with current climate, and should more rapidly track climatic changes. We tested these hypotheses using datasets from 1988 and 2006 containing all European dragon- and damselfly species. Bioclimatic envelope models showed that lentic species were closer to climatic equilibrium than lotic species. Furthermore, the models over-predicted lotic species ranges more strongly than lentic species ranges, indicating that lentic species track climatic changes more rapidly than lotic species. These results are consistent with the proposed hypothesis that habitat persistence affects the evolution of dispersal.     

Jumping ability is related to change of direction ability in elite handball players

PurposeThis study investigated the relationship between vertical and horizontal jumping ability and change of direction (COD) to measure athletic performance in 51 elite male handball players.Scope.Countermovement jump (CMJ), peak power, and standing long jump (SLJ) were measured. Participants performed a 20-m sprint test (time measured at 5, 10, and 20 m) and a zigzag test (COD: 135°, 90°, and 45°). The COD deficit, an index of the time required for COD, was calculated. The correlations between CMJ height and zigzag test times were relatively large (at 135°, r =  − 0.607; at 90°, r =  − 0.594; at 45°, r =  − 0.613; p < 0.01), whereas those between CMJ height and COD deficit were moderate (at 135°, r =  − 0.399, p < 0.01; at 90°, r =  − 0.350, p < 0.05; at 45°, r =  − 0.323, p < 0.05). SLJ showed a negative moderate correlation with COD deficit (at 135°, r =  − 0.439, p < 0.01; at 90°, r =  − 0.469, p < 0.01; at 45°, r =  − 0.380, p < 0.01).ConclusionsThis study is the first to analyse SLJ ability and COD deficit parameters of handball players. We found that SLJ ability is moderately related to COD time and deficit; therefore, SLJ measurement may be a useful predictor of athletic performance.     

A technique to measure the ability of the human nose to warm and humidify air.

To assess the ability of the nose to warm and humidify inhaled air, we developed a nasopharyngeal probe and measured the temperature and humidity of air exiting the nasal cavity. We delivered cold, dry air (19-1 degrees C, <10% relative humidity) or hot, humid air (37 degrees C, >90% relative humidity) to the nose via a nasal mask at flow rates of 5, 10, and 20 l/min. We used a water gradient across the nose (water content in nasopharynx minus water content of delivered air) to assess nasal function. We studied the characteristics of nasal air conditioning in 22 asymptomatic, seasonally allergic subjects (out of their allergy season) and 11 nonallergic normal subjects. Inhalation of hot, humid air at increasingly higher flow rates had little effect on both the relative humidity and the temperature of air in the nasopharynx. In both groups, increasing the flow of cold, dry air lowered both the temperature and the water content of the inspired air measured in the nasopharynx, although the relative humidity remained at 100%. Water gradient values obtained during cold dry air challenges on separate days showed reproducibility in both allergic and nonallergic subjects. After exposure to cold, dry air, the water gradient was significantly lower in allergic than in nonallergic subjects (1,430 +/- 45 vs. 1,718 +/- 141 mg; P = 0.02), suggesting an impairment in their ability to warm and humidify inhaled air.     

Cryoprotectant and freezing-process alter the ability of chicken sperm to acrosome react

Sperm surviving after freezing-thawing is usually 40-50% of the initial population. Damage during this process affects both fertilizing ability and its duration in avian species. However, the effect of cryopreservation on the sperm ability to undergo the acrosome reaction, the initial event of fertilization, is still in question in birds. In this paper, the influence of cryoprotectant (glycerol and dimethylacetamide-DMA) and of two different cryopreservation processes (pellets or straws) on the ability of rooster sperm to acrosome react (AR measured with PNA-FITC) was studied. Motility parameters (CASA) and plasma membrane integrity (propidium iodide exclusion) were also measured. The addition of cryoprotectants (CPA) immediately provoked a dramatic decrease in the ability of sperm to undergo the acrosome reaction, glycerol being more harmful than DMA. The cryoprotectant removal was also harmful. The other parts of the freezing process further decreased the ability to AR. Motility was affected to a lesser extent by CPA presence although plasma membrane integrity was not altered. The DMA/rapid freezing procedure was the most harmful for plasma membrane integrity. Taken together, these results show that AR is more dramatically altered by CPA presence than motility and membrane integrity and CPA provokes a more pronounced effect than the freezing-thawing process especially in the case of using glycerol/slow freezing process.     

Improving the scale and precision of hypotheses to explain root foraging ability

Background

Numerous hypotheses have been proposed to explain the wide variation in the ability of plants to forage for resources by proliferating roots in soil nutrient patches. Comparative analyses have found little evidence to support many of these hypotheses, raising the question of what role resource-foraging ability plays in determining plant fitness and community structure.

Scope

In the present viewpoint, we respond to Grime''s (2007; Annals of Botany 99: 1017–1021) suggestion that we misinterpreted the scope of the scale–precision trade-off hypothesis, which states that there is a trade-off between the spatial scale over which plant species forage and the precision with which they are able to proliferate roots in resource patches. We use a meta-analysis of published foraging scale–precision correlations to demonstrate that there is no empirical support for the scale–precision trade-off hypothesis. Based on correlations between foraging precision and various plant morphological and ecophysiological traits, we found that foraging precision forms part of the ‘fast’ suite of plant traits related to rapid growth rates and resource uptake rates.

Conclusions

We suggest there is a need not only to examine correlations between foraging precision and other plant traits, but to expand our notion of what traits might be important in determining the resource-foraging ability of plants. By placing foraging ability in the broader context of plant traits and resource economy strategies, it will be possible to develop a new and empirically supported framework to understand how plasticity in resource uptake and allocation affect plant fitness and community structure.Key words: Root foraging, phenotypic plasticity, scale, precision, resource uptake strategies, traits     

Exploration of the ability of Coleus blumei to accumulate aluminum

In this study, the capacity of an ornamental species (Coleus blumei) to extract and accumulate aluminum was evaluated. The analyzed parameters were amount of soluble aluminum, radical growth, tolerance rate, bioaccumulation factor, and tissues aluminum concentration. The main limiting factor for aluminum accumulation is the availability of the metal. However, Coleus blumei can grow and accumulate up to 1445.7 mg kg(-1) of aluminum dry base. This plant can play an important role in the treatment of polluted water with metals, since it can grow in conditions with a pH of around 4.8. The aluminum tolerance rate showed for this plant ranged between 18.8% and 25%. Therefore, this species behaves as a non-accumulator, even though the bioaccumulation factor was 3098.5 L kg(-1).     

Cloning of nocardioform DNA conferring the ability to inactivate rifampicin

A novel mechanism of resistance to rifampicin has recently been reported in which this antibiotic is inactivated. Here we describe the cloning of DNA from a nocardiofrom strain conferring this ability to inactivate rifampicin. Cloning was on the basis of complementation, as an increased resistance to the antibiotic. The genetic information was on a 8.3-kb BglII fragment.     

Factors affecting the ability of isolated Plasmodium knowlesi merozoites to attach to and invade erythrocytes

Plasmodium knowlesi merozoites were prepared by the polycarbonate sieving method of Dennis, Mitchell, Butcher & Cohen (1975). Merozoite function was assayed by their attachment to and invasion of rhesus erythrocytes at 37 degrees C. The early merozoites from the culture chamber were the most invasive, although maximum numbers of merozoites appeared later. Merozoites were most stable when incubated at room temperature (23 degrees C). At 37 and 0 degrees C invasiveness rapidly declined to zero. Attachment was rapidly lost at 37 degrees C but was retained at 0 degrees C. Attachment was unchanged in the pH range 6.8--7.9 but invasion was reduced at pH 7.9. The presence of L-fucose, D-galactose, D-glucose, D-mannose, N-acetyl-D-galactosamine or N-acetyl-D-glucosamine did not reduce invasion. Attachment and invasion were greatly reduced or abolished by the presence of 2.5 mM EDTA or EGTA, by lactoperoxidase-catalysed iodination of the merozoites, or by treatment of the merozoites with trypsin at a concentration of 1 micrograms/ml or greater for 10 min at 23 degrees C.