Exchanges of sodium and chloride at low salinities by Nereis diversicolor (Annelida, Polychaeta).
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1. Experiments to compare the exchange (total influx) of sodium and chloride in the polychaete Nereis diversicolor in steady-state adaptation to very low salinities are reported. 2. The Na-uptake mechanism shows a high affinity for sodium, reaching half the maximal uptake rate at an external Na-concentration of 8-10 mM/liter (ca. 2% SW), and becomes "saturated" or reaches a plateau of uptake at concentrations of 40-50 mM/liter (ca. 10% SW) up to ca. 350 mM/liter (75% SW), above which Na-exchange is proportional to the external concentration. 3. The Cl-uptake curve differs from the Na-uptake curve in showing a relative depression at very low salinities before reaching "saturation" at Cl-concentrations of 50-60 mM/liter (ca. 10% SW). Cl-uptake becomes proportional to external concentration in salinities of 50% SW or greater, suggestive of passive diffusion in the ionic and osmotic conforming range. 4. It is shown that the permeability of the body wall, both to Na and to Cl, is reduced at very low salinities, thus destroying one of the assumptions upon which a previously-presented balance-sheet for chloride exchanges in N. diversicolor was based (Smith, 1970a). 5. Attempts to demonstrate an activation of the Na-uptake mechanism at very low salinities were inconclusive; reduction of body-wall permeability to sodium masks any possible activation. 6. It is suggested that the inside-negative body-wall potential is related to the depression of the Cl-uptake curve in salinities below 10% SW. (+info)
Enhancement of compliance among patients with hypertension.
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Studies of patient compliance with medical advice consistently demonstrate a high level of noncompliance. Not following recommendations can have serious negative consequences in the management of disease. This study was an assessment of the effect on compliance of a longitudinal, individualized educational program for patients with hypertension in a managed care setting. A before-and-after self-paired design was used to assess the behavior of 107 patients with hypertension. Trained nurses using an interactive interview format reinforced prescribed treatment and provided appropriate printed material to participants. Brief telephone follow-up interviews at prescribed intervals were used to elicit problems, provide additional education, and reinforce compliance behaviors. Most of the patients who participated showed a statistically significant (P < 0.01) decrease in both systolic and diastolic blood pressure. There was also an effect on various recommended behaviors, including compliance with medication taking, ideal body weight, salt restriction, stress, and exercise. A statistically significant relation existed between improved compliance with individual behavior changes and decreased blood pressure (P < 0.01). Elderly persons were particularly likely to show statistically significant reductions in blood pressure (75.4% versus 50.0%). A chi 2 test indicated that those differences were significant at the 0.01 level. A relatively inexpensive, office-based educational protocol can have a statistically significant effect on treatment compliance among patients with hypertension. The intervention has particular implications for geriatric patients, whose high blood pressure is disproportionately represented. (+info)
Effect of phospholipase A2 digestion on the conformation and lysine/fibrinogen binding properties of human lipoprotein[a].
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In vitro hydrolysis of human lipoprotein[a] (Lp[a]) by phospholipase A2 (PLA2) decreased the phosphatidylcholine (PC) content by 85%, but increased nonesterified fatty acids 3.2-fold and lysoPC 12.9-fold. PLA2-treated Lp[a] had a decreased molecular weight, increased density, and greater electronegativity on agarose gels. In solution, PLA2-Lp[a] was a monomer, and when assessed by sedimentation velocity it behaved like untreated Lp[a], in that it remained compact in NaCl solutions but assumed the extended form in the presence of 6-amino hexanoic acid, which was shown previously to have an affinity for the apo[a] lysine binding site II (LBS II) comprising kringles IV5-8. We interpreted our findings to indicate that PLA2 digestion had no effect on the reactivity of this site. This conclusion was supported by the results obtained from lysine Sepharose and fibrinogen binding experiments, in the presence and absence of Tween 20, showing that phospholipolysis had no effect on the reactivity of the LBS-II domain. A comparable binding behavior was also exhibited by the free apo[a] derived from each of the two forms of Lp[a]. We did observe a small increase in affinity of PLA2-Lp[a] to lysine Sepharose and attributed it to changes in reactivity of the LBS I domain (kringle IV10) induced by phospholipolysis. In conclusion, the extensive modification of Lp[a] caused by PLA2 digestion had no significant influence on the reactivity of LBS II, which is the domain involved in the binding of apo[a] to fibrinogen and apoB-100. These results also suggest that phospholipids do not play an important role in these interactions. (+info)
Promotion of antibiotic production by high ethanol, high NaCl concentration, or heat shock in Pseudomonas fluorescens S272.
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A stress imposed by a continuous feed of high ethanol, high NaCl concentration, or a high temperature shock increased antibiotic production by several times in Pseudomonas fluorescens S272. A tentative bioassay showed that the stress caused about 40-fold elevation in the autoinducer activity. Addition of synthetic autoinducers, N-(3-oxododecanoyl)-L-homoserine lactone or N-(3-oxohexanoyl)-L-homoserine lactone at a concentration of more than 100 micrograms/l to a non-stressed culture also increased the antibiotic production by several times. These results suggested that the antibiotic production in P. fluorescens S272 was regulated by N-acyl-homoserine lactone and the promotive effect by stress occurred through any function that increased the autoinducer production. (+info)
Characteristics of time-dependent PCO2 tonometry in the normal human stomach.
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Factors that affect PCO2 measurement in balloon saline during gastrointestinal tonometry are unclear. They include carbon dioxide diffusion rate, correction factors for calculation of equilibrium PCO2 from measurements at saline dwell times that are shorter than needed for full equilibration, role of blood-gas analyser bias during ex vivo PCO2 measurements in saline, and normal values for intragastric PCO2 (PiCO2) and intramucosal pH (pHi) at equilibrium, and their differences from blood values. In a laboratory study, normal PCO2 changes in a saline-filled tonometer balloon placed in a saline bath at constant PCO2 were described by a non-linear model, with a half-time of mean 4.4 min and 95% equilibration at mean 83 min. In a study in 20 healthy volunteers, PiCO2 build up in a saline-filled tonometer balloon placed in the stomach, measured at dwell times of 10, 20, 30 and 60 min, was slightly (P < 0.05) slower than in vitro, with a half-time of mean 5.8 min and 95% equilibration at mean 110 min. Correction factors to derive equilibrium PiCO2 at short dwell times and independently from blood-gas analyser bias were calculated. The factors differed (P < 0.05) from those currently provided by the manufacturer. Normal threshold values (mean) were: equilibrium PiCO2 < or = 6.6 kPa, pHi > or = 7.33, PiCO2 to blood PCO2 difference < or = 1.1 kPa and pH difference > or = -0.06. PiCO2 did not differ from, and was directly related to, blood PCO2. These values provide a reference base for other studies and show that gastric mucosal PCO2 depends on alveolar ventilation if blood flow is adequate. (+info)
Gastric tonometry: in vivo comparison of saline and air tonometry in patients with cardiogenic shock.
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Measurement of gastric intramucosal pH (pHi) has been advocated to assess gastric perfusion. Regional PCO2 (rPCO2) values are measured using saline tonometry (rsPCO2) and more recently using air tonometry (raPCO2). We compared 237 measurements of saline and air tonometry in 19 consecutive, severely ill patients (mean age 59 (range 31-76) yr, 19 males, APACHE II 22 +/- 7) with cardiogenic shock. Equilibration period was set to 90 min. Nineteen independent paired samples of mean raPCO2 and mean rsPCO2 of each patient showed good correlation (r = 0.93, P < 0.001). Mean raPCO2 was 6.5 (1.8) kPa and mean rsPCO2 6.8 (2.4) kPa. PCO2 measured by saline was significantly higher than that measured by air (P < 0.05). Bland and Altman analysis showed a bias (mean rsPCO2-mean raPCO2) of 0.3 kPa and a precision of 1.2 kPa. Agreement between the two methods decreased with increasing rPCO2 concentrations. Although air tonometry of rPCO2 is a promising technique, a systematic disagreement with saline tonometry at high rPCO2 values requires further investigation and cautious interpretation of these values. (+info)
Inflammatory response after inhalation of bacterial endotoxin assessed by the induced sputum technique.
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BACKGROUND: Organic dusts may cause inflammation in the airways. This study was performed to assess the usefulness of the induced sputum technique for evaluating the presence of airways inflammation using inhaled endotoxin (lipopolysaccharide) as the inducer of inflammation. METHODS: To characterise the inflammatory response after inhalation of endotoxin, 21 healthy subjects inhaled 40 micrograms lipopolysaccharide and were examined before and 24 hours after exposure. Examinations consisted of a questionnaire for symptoms, spirometric testing, blood sampling, and collection of induced sputum using hypertonic saline. Eleven of the subjects inhaled hypertonic saline without endotoxin exposure as controls. Cell counts, eosinophilic cationic protein (ECP), and myeloperoxidase (MPO) were determined in blood and sputum. RESULTS: A significantly higher proportion of subjects reported respiratory and general symptoms after endotoxin inhalation. MPO and the number of neutrophils in the blood were higher and spirometric values were decreased after the lipopolysaccharide challenge. In the sputum MPO, ECP, and the numbers of neutrophils and lymphocytes were higher after the lipopolysaccharide challenge. No significant differences were found after the inhalation of hypertonic saline compared with before, except for a significantly lower number of lymphocytes in the sputum. CONCLUSIONS: The results support previous studies that inhaled endotoxin causes an inflammation at the exposure site itself, as well as general effects. Sampling of sputum seems to be a useful tool for assessing the presence of airways inflammation, and the inhalation of hypertonic saline used to induce sputum did not significantly interfere with the results found after inhalation of lipopolysaccharide. (+info)
Nanoelectrospray--more than just a minimized-flow electrospray ionization source.
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The comparison between electrospray ionization (ESI) mass spectra from NaCl solutions with and without analyte obtained under ionspray and nanospray conditions reveals different mass spectral behavior of the two ESI techniques. This can be attributed to the different initial droplet sizes which are in the microns range for ionspray, while in nanospray they are believed to be about one order of magnitude smaller. In the context of the widely accepted uneven-fission model, nanospray would then enter one fission generation later; in addition, a higher initial droplet surface charge density in nanospray results in early fissions without extensive evaporation and thus increase in sample and salt concentration. This rationalizes that ionspray spectra closely resemble nanospray spectra from solutions with about one order of magnitude higher salt concentrations, showing a higher tolerance of nanospray towards salt contamination. When the analyte is a peptide (in a solution containing a high molar surplus of salt), molecule ion formation effectively competes with salt cluster ion formation; when the analyte is a sugar, it is detectable beside a high salt concentration only with nanospray, indicating the supporting effect of surface activity on ion release in the case of peptides. A model is presented which explains the different mass spectral behaviour of ionspray and nanospray by suggesting different "predominant fission pathways" depending on the size of the initial droplets. (+info)