Pseudomonas stutzeri MJL19, a rhizosphere-colonizing bacterium that promotes plant growth under saline stress.

AIMS: The aim of this study was to find and use rhizobacteria able to confer plants advantages to deal with saline conditions. METHODS AND RESULTS: We isolated 24 different bacterial species from the rhizosphere of halophyte plants growing in Santiago del Estero, Argentina salt flat. Four strains were selected upon their ability to grow in salinity and their biochemical traits associated with plant growth promotion. Next, we tested the adhesion on soybean seeds surface and root colonization with the four selected isolates. Isolate 19 stood out from the rest and was selected for further experiments. This strain showed positive chemotaxis towards soybean root exudates and a remarkable ability to form biofilm both in vitro conditions and on soybean roots. Interestingly, this trait was enhanced in high saline conditions, indicating the extremely adapted nature of the bacterium to high salinity. In addition, this strain positively impacted on seed germination, plant growth and general plant health status also under saline stress. CONCLUSIONS: A bacterium isolate with outstanding ability to promote seed germination and plant growth under saline conditions was found. SIGNIFICANCE AND IMPACT OF THE STUDY: The experimental approach allowed us to find a suitable bacterial candidate for a biofertilizer intended to alleviate saline stress on crops. This would allow the use of soil now considered inadequate for agriculture and thus prevent further advancement of agriculture frontiers into areas of environmental value.

Can atom-surface potential measurements test atomic structure models?

van der Waals (vdW) atom-surface potentials can be excellent benchmarks for atomic structure calculations. This is especially true if measurements are made with two different types of atoms interacting with the same surface sample. Here we show theoretically how ratios of vdW potential strengths (e.g., C3(K)/C3(Na)) depend sensitively on the properties of each atom, yet these ratios are relatively insensitive to properties of the surface. We discuss how C3 ratios depend on atomic core electrons by using a two-oscillator model to represent the contribution from atomic valence electrons and core electrons separately. We explain why certain pairs of atoms are preferable to study for future experimental tests of atomic structure calculations. A well chosen pair of atoms (e.g., K and Na) will have a C3 ratio that is insensitive to the permittivity of the surface, whereas a poorly chosen pair (e.g., K and He) will have a ratio of C3 values that depends more strongly on the permittivity of the surface.

Atom diffraction reveals the impact of atomic core electrons on atom-surface potentials.

We measured ratios of van der Waals potential coefficients (C3) for different atoms (Li, Na, K, and Rb) interacting with the same surface by studying atom diffraction from a nanograting. These measurements are a sensitive test of atomic structure calculations because C3 ratios are strongly influenced by core electrons and only weakly influenced by the permittivity and geometry of the surface. Our measurement uncertainty of 2% in the ratio C(3)(K)/C(3)(Na) is close to the uncertainty of the best theoretical predictions, and some of these predictions are inconsistent with our measurement.

Cover slip external cavity diode laser.

A 671 nm diode laser with a mode-hop-free tuning range of 40 GHz is described. This long tuning range is achieved by simultaneously ramping the external cavity length with the laser injection current. The laser output pointing remains fixed, independent of its frequency because of the cover slip cavity design. This system is simple, economical, robust, and easy to use for spectroscopy, as we demonstrate with lithium vapor and lithium atom beam experiments.

Pseudomonas protegens CS1 from the lemon phyllosphere as a candidate for citrus canker biocontrol agent.

Citrus canker is a worldwide-distributed disease caused by Xanthomonas citri subsp. citri. One of the most used strategies to control the disease is centred on copper-based compounds that cause environmental problems. Therefore, it is of interest to develop new strategies to manage the disease. Previously, we reported the ability of the siderophore pyochelin, produced by the opportunistic human pathogen Pseudomonas aeruginosa, to inhibit in vitro several bacterial species, including X. citri subsp. citri. The action mechanism, addressed with the model bacterium Escherichia coli, was connected to the generation of reactive oxygen species (ROS). This work aimed to find a non-pathogenic strain from the lemon phyllosphere that would produce pyochelin and therefore serve in canker biocontrol. An isolate that retained its capacity to colonise the lemon phyllosphere and inhibit X. citri subsp. citri was selected and characterised as Pseudomonas protegens CS1. From a liquid culture of this strain, the active compound was purified and identified as the pyochelin enantiomer, enantio-pyochelin. Using the producing strain and the pure compound, both in vitro and in vivo, we determined that the action mechanism of X. citri subsp. citri inhibition also involved the generation of ROS. Finally, the potential application of P. protegens CS1 was evaluated by spraying the bacterium in a model that mimics the natural X. citri subsp. citri infection. The ability of P. protegens CS1 to reduce canker formation makes this strain an interesting candidate as a biocontrol agent.

Rat renal and plasma prorenin are activated in vitro by different mechanisms.

The aim of the present study was to purify and identify a plasma protein fraction (PreR-Co) involved in renal prorenin activation and to explore its capacity to process plasma prorenin. PreR-Co was obtained from plasma as a single electrophoretic band by (NH(4))(2)SO(4) precipitation, Sephacryl S-200 HR gel filtration, anti-rat albumin immunoaffinity, and ion-exchange chromatography. The amidase, esterase, and kallikrein activities of PreR-Co were studied, as was its N-terminal amino acid sequence. Rat kidney extract or plasma (normal or previously treated with acid to pH 2.8) were incubated with PreR-Co for 15 minutes at 37 degrees C. Renin concentration was measured by incubation with homologous angiotensinogen. The same protocol was repeated with samples activated by trypsin. The N-terminal amino acid sequence was IIGGSMDAKGSFP, which had a homology of 90% with the beta-chain of haptoglobin, 69% with serine-proteases, and 65% with kallikreins. The renin concentration in rat kidney extract was 34+/-4 ng of angiotensin I (Ang I). mg of tissue(-1). h(-1). After PreR-Co or trypsin treatments, renin concentrations were 211+/-7 and 110+/-11 ng of Ang I. mg of tissue(-1). h(-1), respectively. The plasma renin concentration in normal plasma was 67.6+/-13.3 ng of Ang I. mL(-1). h(-1), and no significant difference was observed after PreR-Co treatment. However, a significant increase (202.8+/-7.8 ng of Ang I. mL(-1). h(-1); P<0.01) was found after trypsin treatment. The isolated PreR-Co acts on renal prorenin but not on plasma prorenin. These results suggest that active renin is processed in the kidney by a circulating enzyme that may have a role in the regulation of circulating renin.

Isoproterenol decreases protein permeability in edematous isolated rabbit lungs: estimation of PS and sigma.

The objective of the present study was to determine whether the ability of the beta-adrenergic agonist isoproterenol to attenuate pulmonary edema occurs via a permeability and/or hemodynamic mechanism. In isolated perfused rabbit lungs, the restrictive property of the vascular barrier to the movement of fluid and protein was assessed by measurements of the capillary filtration coefficient (Kf) and the transvascular clearance of 125I-labeled albumin, respectively. Regression analysis of albumin clearance vs. transvascular fluid flux was performed to estimate the permeability-surface area product (PS) and the reflection coefficient (sigma) by use of the linear or nonlinear flux equation. Arterial, capillary, and venous pressures and resistances, weight gain, and the wet-to-dry weight ratio were also assessed. Isoproterenol (8 ng.ml-1.min-1) attenuated the arachidonic acid (4 mg)-induced increases in fluid flux, wet-to-dry weight ratio, albumin clearance, and PS and the decrease in sigma. Isoproterenol had no effect on the increase in Kf, and there was no correlation between capillary pressure and fluid flux in any of the four groups. Regression analysis revealed that the non-linear flux equation provided estimates of PS and sigma that more accurately described the statistical differences in albumin clearance among the groups studied than the linear flux equation. These findings demonstrate that isoproterenol attenuated the increased transvascular flux of albumin in edematous lungs by modifying the protein permeability of the vascular barrier.

Plasma fibronectin therapy and lung protein clearance with bacteremia after surgery.

Plasma fibronectin modulates macrophage phagocytic function and can also incorporate into the insoluble tissue pool of fibronectin where it influences endothelial cell adhesion and tissue integrity. We studied the effect of postoperative bacteremia on lung protein clearance in relation to plasma fibronectin levels using the unanesthetized sheep lung lymph fistula model and the effect of infusion of purified human plasma fibronectin on lung protein clearance. Sheep received live Pseudomonas aeruginosa (5 X 10(8) iv) at a time of normal plasma fibronectin (590 +/- 37 micrograms/ml) or 5 days later at a time corresponding to elevation of plasma fibronectin (921 +/- 114 micrograms/ml). After the first bacterial challenge, there was a 22% decrease (P less than 0.05) in plasma fibronectin. Lung lymph flow (QL) initially increased 308% (P less than 0.05) by 2 h (0 h = 4.7 +/- 1.1 ml/h; 2 h = 14.4 +/- 3.5 ml/h), and the total protein lymph-to-plasma concentration ratio (L/P) declined. This was followed by a sustained second phase response over 3-12 h which was characterized by a 202-393% elevation in QL (P less than 0.05), an increase in the L/P ratio, and a 240-480% (P less than 0.05) increase in lung transvascular protein clearance (TVPC = QL X L/P). Sheep with elevated fibronectin levels also manifested the early (2 h) elevation in QL (P less than 0.05) coupled with a decline in L/P ratio after the second bacterial challenge, but the second-phase increase in TVPC was markedly attenuated. Intravenous infusion of 500 mg of human plasma fibronectin into normal sheep to elevate the fibronectin level comparable to that in the hyperfibronectinemic sheep also attenuated (P less than 0.05) the second-phase (3-12 h) increase in lung protein clearance with sepsis. Thus elevation of plasma fibronectin during postoperative Gram-negative bacteremia may protect the lung vascular barrier. This response may be mediated by either fibronectin's opsonic support of phagocytic function or its influence on lung endothelial cell adhesion.

Simultaneous measurement of fluid and protein permeability in isolated rabbit lungs during edema.

Fluid conductance and protein permeability have been studied in isolated perfused lung models of pulmonary edema. However, previous studies have not investigated changes of both fluid conductance and protein permeability in the same isolated lung preparation after injury. Arachidonic acid (AA) metabolites are involved in the inflammatory processes that lead to the development of pulmonary edema. The hemodynamic effects of AA have been well established; however, controversy exists concerning the ability of AA to alter the permeability of the pulmonary microvasculature to fluid and protein. The purpose of this study was to simultaneously determine whether transvascular fluid conductance and protein permeability are increased in isolated perfused rabbit lungs with pulmonary edema induced by AA. Indomethacin (80 microM) was added to the perfusate to inhibit the hemodynamic effects of AA and produce a pressure-independent model of pulmonary edema. Fluid conductance was assessed by determination of the capillary filtration coefficient (Kf), and protein permeability was evaluated by measurement of 125I-albumin clearance. The injection of AA (3 mg/200 ml of perfusate) into the pulmonary arterial catheter resulted in an increase in lung weight over the remaining 30-min experimental period. Kf (microliter.s-1 x cmH2O-1 x g dry lung-1) was increased (P < 0.05) in AA-treated lungs at 10 and 30 min post-AA injection when compared with control lungs and baseline values (determined 10 min before AA injection). Albumin clearance was also greater (P < 0.05) in lungs that received AA. 125I-albumin clearance was measured at different rates of fluid flux produced by elevation of venous pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Thrombin increases fluid flux in isolated rat lungs by a hemodynamic and not a permeability mechanism.

Alpha-Thrombin increases endothelial protein permeability in vitro and induces weight gain in the isolated perfused lung. The objectives of this study were to determine whether thrombin increases endothelial permeability of the isolated perfused rat lung and whether a change in permeability or hemodynamics mediates the gain in lung weight. Endothelial protein permeability was assessed by regression analysis of 125I-labeled albumin clearance vs. fluid flux to determine the permeability-surface area product (PS) and the reflection coefficient (sigma). Thrombin (5 x 10(-8) or 5 x 10(-7) M) did not alter protein permeability from the control values of PS and sigma. Thrombin caused an overall increase in transvascular fluid flux, as depicted by a gain in lung weight. Pulmonary arterial and capillary pressures and arterial and venous resistances increased by 10 min after thrombin injection, and lung weight decreased due to arterial constriction. From 10 to 50 min, pressures and resistances decreased, but capillary pressure and venous resistance decreased to a lesser extent and, as a result, lung weight increased. Pretreatment with BQ-123, an endothelin-receptor antagonist, attenuated the sustained increases in pressures and resistances and the rate of lung weight gain. Indomethacin, a cyclooxygenase inhibitor, had no effect. These findings indicate that the increase in lung weight induced by thrombin results from an elevation of capillary pressure mediated, in part, by endothelin and is not due to an increase in endothelial protein permeability of the isolated perfused rat lung.

Oxidant-increased endothelial permeability: prevention with phosphodiesterase inhibition vs. cAMP production.

The present objective was to determine whether hydrogen peroxide (H(2)O(2)) increases transvascular albumin clearance and lung weight in an isolated rat lung and whether posttreatment with cAMP-enhancing agents can prevent these increases. Transvascular albumin clearance was assessed by (125)I-labeled albumin clearance ((125)I-albumin flux/perfusate concentration of (125)I-albumin) at a given fluid filtration. Nonlinear regression analysis of transvascular albumin clearance vs. fluid filtration yielded values for the permeability-surface area product (PS) and the reflection coefficient (sigma). H(2)O(2) decreased sigma from a control value of 0.93 to 0.38, did not change PS, and increased lung weight. Posttreatment with isoproterenol, a beta(2)-adrenergic-receptor agonist, reduced the H(2)O(2)-induced decrease in sigma to 0.65 and augmented the increase in lung weight. Posttreatment with CP-80633, a phosphodiesterase 4 inhibitor, further reduced the H(2)O(2)-induced decrease in sigma to 0.79 and blocked the rise in lung weight. In the presence of isoproterenol or CP-80633, H(2)O(2) increased PS. Therefore, H(2)O(2) increased the convective and diffusive clearances of albumin across an intact pulmonary vasculature. Furthermore, inhibition of cAMP metabolism more effectively attenuated the H(2)O(2)-induced increases in convective albumin clearance and lung weight as compared with stimulation of cAMP production.

Steroid priming promotes oxytocin-induced norepinephrine release in the ventromedial hypothalamus of female rats.

In vivo microdialysis was used to detect norepinephrine (NE) release in the ventromedial hypothalamus of estradiol (E2)- or E2 plus progesterone (P)-treated female rats injected with 1.0 IU of oxytocin (OXY). Dialysates were collected before and after OXY administration on 3 consecutive days and analyzed for NE content by high performance liquid chromatography with electrochemical detection. After the last sample was collected on day 1, animals were injected with 3 micrograms E2 benzoate or oil. On day 3, E2-primed animals received 200 micrograms of P and control females received oil prior to OXY administration. OXY administration did not induce NE release on day 1. When OXY was administered to animals that received E2 approximately 20 h earlier, increased release of NE was not consistently seen. In contrast, E2-primed animals that received P on day 3 displayed significant increases in the release of NE after OXY administration compared to their own basal levels and to NE levels in control animals. To distinguish whether E2 priming is sufficient to promote OXY-induced release of NE without the addition of P, NE content of VMH dialysates in a second group of animals was examined following exposure to vehicle or E2 alone. When OXY was administered 24 or 48 h after estrogen priming, only 1 of 4 E2-primed females had modestly elevated dialysate NE levels. To evaluate the interactions between OXY and NE in the regulation of reproductive behavior, lordosis responses were observed in hormone-primed female rats receiving systemic injections of OXY, the alpha 1-adrenoceptor antagonist prazosin, or both OXY and prazosin.(ABSTRACT TRUNCATED AT 250 WORDS)

Progestin receptors in the ventromedial nucleus of the hypothalamus and arcuate nucleus-median eminence are decreased by idazoxan.

Steroid-dependent lordosis behavior in ovariectomized (OVX) guinea pigs is attenuated by alpha 1- and/or alpha 2-noradrenergic (NE) receptor antagonists. Correlated with the decrease in lordosis after alpha 1-NE receptor blockade by prazosin is a decrease in 'cytosol' progestin receptors in the ventromedial hypothalamic nucleus (VMN). We examined whether a presumed alpha 2-NE receptor blocker (idazoxan, IDA) also affects progestin receptors. A decrease in 'cytosol' progestin receptors was found after IDA treatment of OVX, estrogen-treated guinea pigs in the VMN and the arcuate nucleus-median eminence (ARC-ME). Apparently, either prazosin or IDA can inhibit lordosis behavior and decrease 'cytosol' progestin receptors in the VMN. In contrast, idazoxan but not prazosin, decrease 'cytosol' progestin receptors in the ARC-ME.

Effects of non-competitive NMDA receptor antagonists on reproductive and motor behaviors in female rats.

MK-801 and dextrorphan, selective non-competitive antagonists at N-methyl-D-aspartate (NMDA) receptors, were used to evaluate the effect of NMDA receptor blockade on sexual and motor behaviors in female rats. Ovariectomized rats were treated with estradiol benzoate (EB) for 48 or 72 h followed by progesterone (P) 3.5-4 h before testing the animals for sexual receptivity. After testing for estrous responsiveness, the effect of NMDA antagonists on several motor behaviors was also assessed. Lordosis frequency and intensity were inhibited in animals that received 0.5 mg/kg MK-801 30 min before EB; the same dose of MK-801 was relatively ineffective when administered 24 h after EB. In neither case did MK-801-treated females differ from controls when motor behaviors were assessed after mating tests. When 30 mg/kg dextrorphan, a short-acting NMDA antagonist, was administered 15 min before P, sexual behavior was not blocked. However, both 0.05 mg/kg MK-801 and 30 mg/kg dextrorphan suppressed ongoing female sexual behavior within 30 min in animals made receptive with EB and P. These deficits in sexual behavior were associated with changes in motor performance. MK-801 (0.1 mg/kg) and dextrorphan (30 mg/kg) abolished movement in the vertical dimension (e.g. jumping and rearing). By contrast, the drugs increased movement in the longitudinal (locomotion) and lateral (circling) dimensions. At 0.2 mg/kg, MK-801 blocked movement in both the vertical and longitudinal dimensions; however, it failed to block circling. Only at 0.4 mg/kg did MK-801 inhibit lateral movements and righting reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Different roles of alpha-noradrenergic receptor subtypes in regulating lordosis.

Ovariectomized guinea pigs were given free estradiol (E) at hr 0 and 28, and progesterone (P) at hr 39. Experiment 1: The alpha-1 noradrenergic antagonist prazosin, but not the alpha-2 noradrenergic antagonist idazoxan, prevented display of lordosis behavior when administered systemically 30 min prior to E injections at either hr 0 or 28, or 30 min prior to both injections. Experiment 2: Multiple injections of idazoxan (i.e., 30 min prior to and 60 and 120 min after each E injection) failed to prevent display of lordosis. Experiment 3: E-primed animals were given a single injection of idazoxan 1 hr before P, or 5 hr after P. In those animals given idazoxan 1 hr before P, display of lordosis was not prevented. However, in animals given idazoxan once lordosis display had begun (i.e., 5 hr after P) ongoing lordosis behavior was blocked. These data suggest differential roles of alpha-noradrenergic receptor subtypes in regulation of lordosis: noradrenergic transmission through the alpha-1 subtype may mediate hormone-priming processes leading to lordosis, whereas transmission through the alpha-2 subtype may modulate ongoing lordosis responses.

Measuring the diabetes knowledge of nurses in long-term care facilities.

A knowledge test was developed by a local diabetes educators' group to evaluate the diabetes knowledge base of 59 nurses currently employed in four long-term care facilities in eastern North Carolina. The test contained items in the following categories: monitoring, medication, hypoglycemia, hyperglycemia, illness care, diet, exercise, foot care, and patient/family education. The results of the diabetes knowledge test were analyzed according to overall test scores as well as scores in each of the selected categories. The overall scores ranged from 42% to 89%, with a group mean of 67% (passing = 70% or higher). The scores in the individual categories ranged from 18.6% for monitoring and 23.8% for medications to 91.5% for patient/family education.

Telephone communications between diabetes clients and nurse educators.

The purpose of this study was to describe the use of telephone communications between diabetes nurse educators (DNEs) and their clients with diabetes. A questionnaire was designed to examine the use of the telephone with diabetes clients from the perspective of DNEs. A total of 465 DNEs across the US were selected using a systematic sample from the membership directory of the American Association of Diabetes Educators. A total of 247 were questionnaires completed and returned (55%). Ninety-one percent of DNEs reported using the phone with clients and averaged 15 phone calls per week. Over 90% frequently reported discussing the following topics with clients: home blood glucose monitoring, hyperglycemia, hypoglycemia, insulin use, and diet. Analysis of telephone users showed that DNE experience and diabetes educator certification were significant factors in the differences observed in the reported topics discussed over the telephone. These findings suggest the need for guidelines for telephone contact with diabetes clients.

The impact of an educational program on improving diabetes knowledge and changing behaviors of nurses in long-term care facilities.

Nursing staffs from two long-term care facilities attended a multisession educational program about the care of residents with diabetes (treatment group). A control group consisted of the nursing staffs from two other similar facilities who did not participate in the educational program. Both groups were given a knowledge pretest and posttest. A chart review also was conducted following the educational intervention to determine any changes in the diabetes care provided by the treatment group. Following the educational program, the treatment group had a significant increase in their mean score on the knowledge test compared with the control group. However, a review of the residents' charts revealed no significant increases in specific behaviors related to diabetes care. The findings suggest that, in addition to educational programs, more focused training concerning diabetes care is needed to improve the care of residents with diabetes in long-term care facilities. Implications for diabetes educators are discussed.