Effect of inspiratory-phase negative pressure breathing on urine flow in man.

We investigated the effect of negative pressure breathing during the inspiratory phase only (intermittent NPB) in 9 healthy male subjects who were in a sitting position and had no food or fluid intake for 12 h before the study. Intermittent NPB was without effect on urine flow and urinary sodium excretion but caused a significant increase in creatinine clearance. Plasma renin activity was significantly reduced, whereas plasma antidiuretic hormone (ADH), atrial natriuretic factor (ANF), and aldosterone levels were unaffected. To determine whether the blunted urinary response to intermittent NPB was a postural phenomenon, the study was repeated in 6 of the subjects while supine. Under these conditions there was a significant increase in urine flow and plasma ANF levels, but no change in all other measured variables. These results are consistent with a role for ANF, but not ADH, in the diuresis seen in supine subjects during NPB.

Comparative effects of Des Leu Angiotensin I and Angiotensin II on AVP secretion from the hypothalamoneurohypophysis and pituitary of the rat.

In the present study we compared the effects of Des Leu Angiotensin I (Des Leu AI) with Angiotensin II (AII) on the secretion of vasopressin (AVP) from the isolated hypothalamoneurohypophyseal system (HNS) and isolated posterior pituitary gland of the rat. Administration of 10(-6)M, 10(-5) M and 10(-4) M Des Leu AI was without significant effect on AVP secretion from the HNS. A similar phenomenon was seen in the posterior pituitary with 10(-6) M and 10(-5) M Des Leu AI, although 10(-4) M significantly increased AVP release. Administration of 10(-6) M AII was without significant effect in either preparation, although 10(-5) M and 10(-4) M AII caused significant dose-dependent increases in AVP secretion over control release that were similar in both the HNS and posterior pituitary gland. These results suggest that Des Leu AI is not a physiologically relevant stimulus of AVP secretion when restricted to this area of the rat brain. They are also consistent with the presence of receptors sensitive to AII in the pituitary gland of the rat.

Hormonal, electrolyte, and renal responses to exercise are intensity dependent.

Previous work indicates that the magnitude and direction of renal responses to exercise depend on the exercise intensity. To examine mechanisms responsible for these findings, renal and hormonal responses were studied in eight healthy male subjects (29.6 +/- 1.9 yr) before and immediately after four 20-min bouts of submaximal exercise (cycle ergometry) at work loads representing 25, 40, 60, and 80% of maximal oxygen consumption. Urine flow, osmotic clearance, glomerular filtration rate, and sodium excretion (UNa+V) all tended to rise at the 25% work load but were markedly reduced at the higher work intensities. Changes in urine flow paralleled changes in glomerular filtration rate (r = 0.91). Plasma vasopressin (ADH), aldosterone, and plasma renin activity tended to increase progressively with increases in work load, with the increases for all hormones reaching statistical significance when the level of exercise reached greater than or equal to 60% of maximal oxygen consumption. However, atrial natriuretic peptide was elevated (P less than 0.05) at all work loads from greater than 1.6-fold of control levels at the 25% work load to greater than 7-fold at the 80% work load. The increase in urine flow (6 of 8 subjects) and UNa+V (7 of 8 subjects) may be due to the increase in atrial natriuretic peptide and/or a 10% suppression (P less than 0.05) of ADH at the 25% work load.(ABSTRACT TRUNCATED AT 250 WORDS)

Exaggerated ANF response to exercise in middle-aged vs. young runners.

Hormonal, electrolyte, and renal responses were measured before, during, and after a marathon (42.2 km) in 14 runners: 8 young (Y) (mean age 27.8 yr) and 6 middle aged (MA) (mean aged 46.7 yr). No differences between groups in prerun values for heart rate (HR), plasma osmolality (OSM), antidiuretic hormone (ADH), aldosterone (ALDO), atrial natriuretic factor (ANF), or plasma renin activity (PRA) were found. Renal and urinary measurements were also similar between groups before the marathon. After 10 km of running, both groups had significant increases in HR, ALDO, ANF, and PRA, while OSM, Na+, and ADH remained unchanged from prerun values. The increase in plasma ANF concentrations at this point was significantly greater in the MA subjects compared with the Y (mean increase 104.1 vs. 42.8 pg/ml, respectively; P less than 0.01). Immediate postmarathon values for OSM, ADH, and Na+ were significantly higher than initial values in both groups, while HR, PRA, and ALDO continued to increase above the elevated levels found at 10 km. ANF values immediately postmarathon remained higher than prerun concentrations but were significantly reduced from those obtained at 10 km. In contrast, HR continued to rise until the completion of the run. These data are consistent with recent reports of an exaggerated ANF response in older subjects in response to central blood volume expansion.

Developmental changes in sodium nitroprusside and atrial natriuretic factor mediated relaxation in the guinea pig aorta.

Sodium nitroprusside (SNP), a nonreceptor mediated stimulant of soluble guanylate cyclase, and atrial natriuretic factor, a receptor-dependent stimulator of particulate guanylate cyclase, mediate relaxation responses by increasing intracellular cGMP. This in vitro study was designed to compare the ontogeny of relaxation responses to SNP and atrial natriuretic factor in the guinea pig thoracic aorta. Aortic rings from fetuses at 55-60 d gestation (term = 68 d), 1- to 3-d-old newborn, and 12-wk-old adult Hartley guinea pigs were mounted in an organ bath, bathed in Kreb's solution, and connected to a force-displacement transducer to measure isometric tension. Relaxation responses to SNP and atriopeptin III were studied with the vessels at optimal resting tension and after preconstriction with an EC85 concentration of norepinephrine. SNP-mediated relaxation showed a significant increase in sensitivity with development among the three age groups (p less than 0.05). Methylene blue, an inhibitor of soluble guanylate cyclase, produced no inhibition of relaxation to SNP in fetal aortae, significantly decreased responses along the straight portion of the concentration-response curve in newborn aortae (p less than 0.05), and significantly shifted the concentration-response curve to the right (p less than 0.05) in adult aortae; but did not prevent vessels from relaxing almost 100% in any age group. However, atriopeptin III-mediated responses were similar in the three age groups and were unaffected by methylene blue. These results suggest that 1) sensitivity to SNP increases with age from fetal through adult life; 2) relaxation mediated by atriopeptin III is similar during development; 3) methylene blue does not affect SNP mediated relaxation in fetuses but progressively decreases sensitivity to SNP in newborns and adults; and 4) methylene blue does not affect atriopeptin III-mediated relaxation in any age group.

Hormonal and renal responses to water drinking in moderately trained and untrained humans.

Endurance exercise training alters the regulation of body fluids. To investigate specifics of these alterations, hormonal, electrolyte, and renal responses to water ingestion (1% of lean body wt) were studied in six moderately trained (T) and 6 untrained (UT) male subjects. No differences between groups for base-line hormonal, electrolyte, or renal measurements were found. After water ingestion, atrial natriuretic factor remained unaltered in both groups. Predrink plasma antidiuretic hormone (ADH) levels of 0.51 +/- (SE) 0.19 (UT) and 0.47 +/- 0.07 microU/ml (T) remained unchanged in the T group but were reduced from min 9 through 90 in the UT group. At 30 min postdrink, UT subjects had lower ADH values than T subjects (0.18 +/- 0.02 vs. 0.33 +/- 0.05 microU/ml), while plasma osmolality was similarly reduced by approximately 3 mosmol/kg in both groups. Urine flow rates increased in both groups from similar values of 0.85 +/- 0.24 (UT) and 0.67 +/- 0.11 ml/min (T) to peak flows of 4.6 +/- 1.6 for UT and 2.7 +/- 1.1 ml/min (T) to peak T, P less than or equal to 0.05) at 60 min postdrink. Urine osmolality was reduced from similar values of 809.1 +/- 62.1 and 867.0 +/- 56.1 mosmol/kg to values of 248.8 +/- 87.6 and 469 +/- 146.1 mosmol/kg for UT and T, respectively (UT vs. T, P less than 0.05), at 60 min. Reduced ADH before reductions in plasma osmolality in the UT but not the T subjects suggests that T subjects have a reduced oropharyngeal inhibition of ADH.(ABSTRACT TRUNCATED AT 250 WORDS)

Hormonal and vascular fluid responses to maximal exercise in trained and untrained males.

The trained condition is associated with alterations in fluid regulation. In attempt to elucidate mechanisms responsible for these differences, resting, postexercise (maximal treadmill exercise of 8-13 min duration), and recovery measurements were made in seven trained (mean peak O2 consumption was 60.5 +/- 1.6 ml.kg-1.min-1) and seven untrained (mean peak O2 consumption was 40.7 +/- 1.7 ml.kg-1.min-1) male subjects. Samples were obtained by venipuncture with subjects seated. No significant differences in resting plasma osmolality (Osm), sodium, potassium, antidiuretic hormone (ADH), aldosterone, renin activity, or atrial natriuretic factor were found between groups. Maximal exercise produced significant increases in all of the above variables. Values immediately postexercise were similar between groups except for plasma Osm and sodium, which were significantly higher in the untrained group. Despite a reduction in plasma volume of equal magnitude in both groups, trained subjects demonstrated an increase in vascular proteins and mean corpuscular volume during exercise. This increase in plasma protein may be an important initiating factor responsible for the elevated plasma volume after 1-h recovery from exercise in the trained group. Lastly, similar ADH responses despite lower Osm in trained subjects may indicate that training increases the sensitivity of ADH to osmotic stimulation.

Cytomegalovirus isolations from cell cultures of human adenocarcinomas of the colon.

Cytomegalovirus was isolated from cell cultures derived from 3 of 16 surgical specimens of adenocarcinomas of the colon. Virus identification was accomplished through electron microscopical, cytochemical, and immunofluorescent procedures.

Effect of polycations on the early stages of reovirus infection.

The polycation DEAE-dextran treatment of HeLa cells was found to interfere with the production of reovirus, appearance of viral cytopathology, and the induction of cytotoxicity by UV-irradiated reovirus. The data obtained showed that while the polycation pre-treatment of cells enhanced virus adsorption to cells, its addition early during virus adsorption or 2 h after infection markedly interfered with virus production. The interference was decreasingly effective when the polycation was added during the later stages of the infectious cycle. Isopycnic CsCl buoyant density ultracentrifugation analyses of infected cytoplasmic extracts revealed that there were more subviral particles formed in untreated infected cells than there were in polycation-treated cells. In vitro uncoating studies with infected cytoplasmic extracts indicated that the polycation did not interfere with the removal of the outer capsid structure of the complete virus, and uncoating occurred only in the presence of the polycation. Electron microscopical examination revealed significantly fewer virus particles present in polycation-treated infected cells. The accumulated data strongly indicate that interference by DEAE-dextran is an early event involving viral penetration. Corollary studies using other polycations, such as polybrene (hexadimethrine bromide and poly-l-lysine, revealed that while they also enhanced virus adsorption, they did not interfere with reovirus production, appearance of viral cytopathology, and the induction of cytotoxicity by UV-irradiated reovirus.