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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hypothesis that a countercurrent multiplier within the intestinal villus increases osmolality in the distal villus tip was tested. Total sodium, potassium, and water content of intestinal tissue samples was measured. The results showed no significant difference in the total Na plus K concentration (millimoles per kilogram H2O +/- SEM) between the villi tips (185.1 +/- 7.7), whole villi (179.8 +/- 5.4), or intestine minus villi (177.2 +/- 1.7). In contrast, in the kidney (where the existence of a countercurrent multiplier has been demonstrated), the renal medulla had a total Na plus K concentration of 284 +/- 17.1 that was significantly more than the renal cortical concentration of 163 +/- 3.1. Villous tissue osmolality should be in osmotic equilibrium with intestinal luminal fluid. Sampling of intestinal luminal fluid revealed a total Na plus K concentration of 145-165 mmol/kg H2O, a figure compatible with normal luminal osmolality of 280-320 mosmol/kg H2O. These results deny the existence of a countercurrent multiplier in the intestinal villus of the dog.
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PMID:No evidence of a countercurrent multiplier in the intestinal villus of the dog. 168 74

After a single-blind, randomized, cross-over protocol using decaffeinated coffee in a control experiment, the effect of an oral 250-mg caffeine dose on plasma immunoreactive atrial natriuretic peptide (ANF) was assessed in eight healthy students who had been on a methylxanthine-free diet for 1 week. One to 2 h after caffeine ingestion, both systolic blood pressure (SBP) and diastolic BP (DBP) increased by 12 mm Hg while heart rate (HR) also tended to increase. An increase in diuresis and in urinary sodium, potassium, and osmol excretion was observed within 1 h. Decaffeinated coffee induced no change in any of these parameters. Plasma epinephrine (EPI) increased gradually from 16.6 +/- 3.2 pg/ml (mean +/- SEM) to 45.1 +/- 7.9 pg/ml within 2 h after caffeine ingestion, but did not change after decaffeinated coffee (p less than 0.001). Plasma norepinephrine (NE), renin activity (PRA), aldosterone, and vasopressin remained unchanged. Plasma ANF was measured by radioimmunoassay (RIA) using an extremely sensitive antiserum (Kd = 10(-12) M) after rapid and virtually complete (90-103%) extraction from plasma. In 0.2 ml plasma, the theoretical detection limit is 1.1 fmol/ml. Normal plasma ANF concentrations in supine subjects were 17.9 +/- 8.1 fmol/ml (mean +/- SD) and 11.0 +/- 3.3 fmol/ml in subjects in the upright position. Plasma ANF levels were not affected by coffee drinking. In conclusion, by using a new and sensitive assay for plasma ANF, we did not find that caffeine-induced diuresis is mediated by ANF.
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PMID:Caffeine-induced diuresis and atrial natriuretic peptides. 169 26

We have previously found that antigenic stimulation of mast cells in the guinea pig superior cervical ganglion leads to membrane depolarization of principal neurons and a long-term increase in the efficacy of ganglionic transmission. In this study experiments were conducted to discern the histological, immunological and pharmacological characteristics of the mast cells within the superior cervical ganglion. Mast cells within the superior cervical ganglion could be stained with toluidine blue or berberine sulfate, the latter indicating that heparin-like molecules were present in the granules. Stainable mast cells were distributed throughout the ganglion with no gross evidence of regional localization. The number of mast cells stained with toluidine blue was reduced significantly (P less than 0.01) in contralateral ganglia that had been exposed to the sensitizing antigen (ovalbumin), indicating antigen-induced degranulation. The superior cervical ganglion contained 208 +/- 6 picomole of histamine (mean +/- SEM, n = 66). Ovalbumin evoked the release of histamine from the superior cervical ganglion in a concentration-dependent fashion. At maximally effective concentrations, ovalbumin released 33 +/- 2% of the total histamine stores (mean +/- SEM, n = 61). Similar values were obtained with antigen-challenged stellate ganglia. A temperature of 37 degrees C and an extracellular calcium concentration of 1 mM was required to elicit optimal antigen-induced responses. In addition to releasing histamine, antigenic stimulation of the ganglion resulted in a 3- to 5-fold increase in the synthesis and release of arachidonic acid metabolites including peptidoleukotriene, thromboxane B2, prostaglandins (PG) E2, F2 alpha, D2, the PGD2 metabolite 9 alpha 11 beta-PGF2, and the prostacyclin metabolite 6-keto PGF1 alpha. Various putative mast cell secretagogues were examined for their ability to activate the superior cervical ganglion mast cell, as indicated by evoked histamine release. In contrast to rat peritoneal mast cells, high concentrations of substance P, compound 48/80, and nerve growth factor failed to stimulate the ganglion mast cells. Preganglionic nerve stimulation, electrical field stimulation of axons and cell bodies, or depolarizing concentrations of potassium chloride also failed to activate the superior cervical ganglion mast cells. These results suggest that substances released by membrane depolarization do not influence the function of the resident mast cells. The results demonstrate that the mast cells within sympathetic ganglia can be actively sensitized to respond to specific antigen. These mast cells are similar to lung parenchymal mast cells with respect to histological, immunological and pharmacological characteristics...
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PMID:Mast cells in the guinea pig superior cervical ganglion: a functional and histological assessment. 169 91

Endothelial cells obtained from human umbilical chord have been studied by the patch clamp method. An ion channel is described that is activated by microM concentrations of histamine and shows a slow run-down in cell-attached patches. After excision, channel activity quickly runs down to zero open probability. In symmetrical potassium concentrations (140 mM K in the bath and the pipette), the single channel conductance is 28 +/- 2 pS and the reversal potential is 0.3 +/- 0.8 mV (mean +/- SEM, n = 4). With 140 mM Na in the pipette, the conductance is 26 +/- 2 pS. A reversal potential of -1.5 +/- 0.9 mV (n = 7) was measured. With 60 mM Ca and 70 mM Na in the pipette, 140 mM K in the bath, the reversal potential was -11 +/- 3 mV, the single channel conductance in 16 +/- 3 pS (n = 5). The single channel conductance in 110 mM Ca (pipette) and 140 mM K (bath) is 8 +/- 2 pS and the reversal potential is -18 +/- 6 mV (n = 3). From analysis of the reversal potentials, a permeation ratio of K:Na:Ca = 1:0.9:0.2 was calculated. This ligand-gated non-selective cation channel in human endothelial cells is Ca permeable and could induce a sustained agonist mediated Ca influx.
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PMID:Permeation properties of a non-selective cation channel in human vascular endothelial cells. 170 Mar 63

Limited availability of donor organs is a major factor restricting the clinical application of lung transplantation. Improvements in preservation techniques are essential for prolonging storage time and improving lung function following transplantation. The present investigation used primary cultures of adult rat alveolar type II cells as a model for evaluating lung-preservation solutions. Type II cells were plated onto tissue-culture plastic at a density 5 x 10(5) cells/cm2 and maintained in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum (D10) for 40 hr. Cells were then exposed to Euro-Collins solution or a low-potassium-dextran solution (LPD). At designated time points, measurements of lactate-dehydrogenase (LDH) release, protein content, and incorporation of 3H-thymidine into cellular DNA were made. During 12 hr of "storage" at 37 degrees C, cells maintained in LPD released less LDH (14.3 +/- 1.2% of cellular total, mean +/- SEM, n = 5) than their counterparts stored in EC (20.6 +/- 1.6%, P less than 0.05). During the 36 hr following a 6-hr exposure to preservative solutions, LPD-treated cells incorporated more thymidine per mg of protein (2566 +/- 419.8 cpm/micrograms protein, mean +/- SEM, n = 6) compared with cells maintained continuously in D10 (1431 +/- 351, P less than 0.05). By contrast, cells exposed to EC incorporated less thymidine (82.2 +/- 62.8 cpm/micrograms protein) than either cells maintained in LPD or D10 (P less than 0.01 for each comparison). These results suggest that LPD solution is less cytotoxic than EC and that LPD enables higher levels of metabolic activity in recovering epithelial cells. In vitro cultures of type II epithelial cells are a useful model system for the study of lung preservation and posttransplantation lung injury.
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PMID:The effect of low-potassium-dextran versus Euro-Collins solution for preservation of isolated type II pneumocytes. 171 65

University of Wisconsin solution has been used successfully in clinical kidney and liver preservation. The object of this study was to determine if low-potassium UW (LPUW) solution could be applied to pulmonary preservation. Rabbit lungs were stored after hypothermic pulmonary artery (PA) flush with four different solutions (group 1: low-potassium dextran (LPD) solution, group 2: high-potassium UW (HPUW) solution, group 3: LPUW solution, group 4: modified Euro-Collins (E-C) solution). The lungs were preserved at 10 degrees C for 30 hr and evaluated in an ex vivo ventilation/perfusion apparatus using fresh pooled venous rabbit blood. Mean PA flush pressures (MFP) during harvesting were significantly lower in groups 1 and 3 (8.1 +/- 1.0 mmHg and 7.3 +/- 0.6 mmHg, respectively; mean +/- SEM) than in groups 2 and 4 (15.5 +/- 1.7 mmHg and 12.3 +/- 0.9 mmHg, respectively). Lungs in groups 1 and 3 showed significantly higher PaO2 (103.5 +/- 8.0 mmHg and 89.3 +/- 7.2 mmHg) than groups 2 and 4 (48.3 +/- 7.7 mmHg, 66.7 +/- 4.7 mmHg). Groups 1 and 3 showed significantly lower wet/dry weight (W/D) ratios after reperfusion (6.21 +/- 0.15 and 6.39 +/- 0.23) than groups 2 and 4 (7.70 +/- 0.57 and 7.13 +/- 0.21, respectively). There were no significant differences in MFP, PaO2, PaCO2, mean pulmonary artery pressure, or W/D ratio between groups 1 and 3. These results suggest that LPUW solution may be as beneficial as LPD solution for pulmonary arterial flush and lung preservation.
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PMID:Low-potassium UW solution for lung preservation. Comparison with regular UW, LPD, and Euro-Collins solutions. 172 Dec 52

One hundred and seventy-two competitors of the Swiss Alpine Marathon, Davos, Switzerland, 1988, volunteered for this research project. Of these volunteers 170 (158 men, 12 women) finished the race (99%). The race length was 67 km with an altitude difference of 1,900 m between the highest and lowest points. Mean age was 39 (SEM 0.8) years. Average finishing times were 8 h 18 min (men) and 8 h 56 min (women). Loss of body mass averaged 3.4% body mass [mean 3.3 (SEM 0.2)%; 4.0 (SEM 0.4)%; men and women, respectively]. Blood samples from a subgroup of 89 subjects (6 women and 83 men) were taken prior to and immediately after completion of the race. Changes in haemoglobin (9.3 mmol.l-1 pre-race, 9.7 mmol.l-1 post-race) and packed cell volume (0.44 pre, 0.48 post-race) were in line with the moderate level of dehydration displayed by changes in body mass. Mean plasma volume decreased by 8.3%. No significant changes in plasma osmolality, sodium, or chloride were observed but plasma potassium did increase by 5% (4.2 mmol.l-1 pre-race, 4.4 mmol.l-1 post-race). Mean fluid consumption was 3290 (SEM 103) ml. Forty-three percent of all subjects, and 33% of those who gave blood samples, complained of gastro-intestinal (GI) distress during the race. No direct relationship was found between the quantity or quality of beverage consumed and the prevalence of GI symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Physiological changes and gastro-intestinal symptoms as a result of ultra-endurance running. 173 4

The effects of carbohydrate loading on relative stress responses of eight male subjects performing intermittent leg exercise at 80% maximum oxygen consumption during headout immersion in 25 degrees C water were tested. Carbohydrate loading increased the number of work cycles completed, with less physical stress compared with that completed following the control diet period. Pre-exercise serum cortisol values were similar on both diets prior to exercise but following exercise control values were greater (1152, 94 vs 858, 77 nmol l-1; mean, SEM). Chromium losses, which have been shown to correlate with stress, were lower during the carbohydrate loading period, 8.6, 1.3 vs 12.4, 2.0 ng h-1, and were correlated with post-exercise serum cortisol. Urinary zinc losses were also lower during carbohydrate loading, while urinary losses of potassium, magnesium and calcium remained constant. Insulin values decreased similarly following exercise in both groups and were not altered by carbohydrate loading. These data demonstrate that carbohydrate loading increases immersion exercise output with less stress as determined by serum cortisol and urinary chromium losses.
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PMID:Effects of carbohydrate loading and underwater exercise on circulating cortisol, insulin and urinary losses of chromium and zinc. 174 6

The effects of whole-body potassium depletion induced by food deprivation on plasma, erythrocyte, and middle gluteal muscle K concentrations was quantified in 16 healthy, adult horses before, during, and at the end of a 7-day period of food deprivation during which water and sodium chloride were available ad libitum. Potassium concentrations were determined by atomic absorption spectroscopy. Plasma K concentration remained constant (3.49 +/- 0.09 mM K/L of plasma; mean +/- SEM) throughout the study. Erythrocyte potassium concentration decreased from 93.10 +/- 1.94 mM K/L of erythrocytes on day 0 to 88.63 +/- 2.39 mM K/L of erythrocytes on day 2 (decrease of 4.8%; P less than 0.05) and thereafter did not change. The K concentration of the middle gluteal muscle decreased from 91.06 +/- 2.96 microM K/g of muscle (wet weight) to 79.61 +/- 2.09 microM K/g of muscle (decrease of 12.6%; P less than 0.05) on day 4 and decreased further on day 7 to 73.62 +/- 1.85 microM K/g of muscle (decrease of 19.2%; P less than 0.05). There was no correlation between the plasma and erythrocyte K concentrations (r = -0.066), the erythrocyte and middle gluteal muscle K concentrations (r = 0.167), or the plasma and middle gluteal muscle potassium concentrations (r = -0.018). The water content of the middle gluteal muscle remained constant (73.23 +/- 0.36%) throughout the study. Erythrocyte membrane potential did not change (-99.26 +/- 0.87 mV) during the study, whereas the magnitude of the membrane potential of the middle gluteal muscle decreased from -105.84 +/- 1.67 mV on day 0 to -100.93 +/- 2.10 mV on day 7 (P less than 0.05).
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PMID:Effect of whole-body potassium depletion on plasma, erythrocyte, and middle gluteal muscle potassium concentration of healthy, adult horses. 176 91

The understanding of the mechanisms underlying the frequency-dependent slow response excitability enhancement has been hindered by the problems inherent in multicellular preparations. These include ion accumulation/depletion in intercellular spaces and difficulties in the spatial control of transmembrane voltage. In the present communication we show that isolated ventricular cells exposed to a depolarizing (high potassium-barium containing) solution present electrophysiological properties similar to those of multicellular preparations: stable resting potential of -45.2 +/- 0.7 mV (mean +/- SEM, N = 57) in 75% of the cells and spontaneous activity in the remaining 25% (maximum diastolic potential of -41.9 +/- 1.2 mV, N = 19); high input resistance and slow response, under current clamp conditions. Under whole cell voltage clamp conditions with -45 mV holding potential, transient outward and delayed potassium currents as well as typical L type calcium channel are present. These cells also present the frequency-dependent excitability enhancement of the slow response, with the threshold stimulus at 1 Hz corresponding to about 50% of that obtained at 0.1 Hz. Thus, isolated ventricular cells constitute a suitable model for the study of frequency-dependent excitability enhancement of the slow response.
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PMID:Frequency-dependent excitability enhancement in isolated ventricular myocardial cells. 182 10


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