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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To investigate the differentiated pattern of efferent sympathetic nerve activity by means of analyzing norepinephrine kinetics in response to sodium restriction, cardiorenal sympathetic activity during rest and mental stress was studied in 12 subjects (33.3 +/- 2.6 years old, SEM) exposed to a low and a normal sodium diet; 5-40 mmol and 160-200 mmol/24 hours, respectively (crossover design). Organ norepinephrine release was calculated from organ plasma flow, arteriovenous plasma concentration gradient across the organ and the organ's fractional extraction of radiolabeled norepinephrine. Body weight and urinary sodium/24 hr fell significantly and urinary potassium/24 hr and both supine and standing blood pressure remained unchanged. Total norepinephrine release to plasma and norepinephrine plasma clearance were similar in both phases (approximately 460 ng/min and 1.90 l/min, respectively). A 138% increase in renal norepinephrine overflow was observed during sodium restriction (from 112 to 267 ng/min, p less than 0.025), which was due to elevated renal vein norepinephrine (434 versus 290 pg/ml, p less than 0.01) because renal plasma flow and renal norepinephrine extraction were unaltered. Similarly, sodium restriction caused a 168% elevation of renal renin secretion (p less than 0.05). Resting cardiac norepinephrine spillover and cardiac norepinephrine reuptake were unchanged between the two salt phases. Total and cardiac norepinephrine release, supine blood pressure, and heart rate increased to about the same extent in response to mental testing regardless of salt phase. In conclusion, sodium restriction induced a differential and physiological increase in resting renal sympathetic nervous activity, leaving cardiac norepinephrine overflow unchanged. Cardiac norepinephrine uptake was normal, which further supports the concept of a true increase of efferent renal nerve activity.
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PMID:Evidence for increased renal norepinephrine overflow during sodium restriction in humans. 237 45

This study was initiated to determine if raised (carcinoid) plasma concentrations of substance P induced jejunal secretion of water and electrolytes. Five dogs had isolated and cannulated 25 cm jejunal segments perfused at 2 ml/min with a neutral, isotonic perfusate. Saline, 1.0 ml, was infused intravenously during basal and recovery periods, while substance P was administered intravenously at 75 ng/kg/min (55 pmol/kg/min) during the four 15 minute experimental periods. Infusion increased plasma SP concentrations from basal (5.8 +/- 1.3 pg/ml) to a mean plateau level of 121.2 +/- 25.2 pg/ml (mean +/- SEM). During SP infusion, intestinal secretion of water, Na+, and Cl- were documented (H2O basal +102 +/- 60 to SP -275 +/- 60; microliter/min; Na+ basal +19.8 +/- 7.2 to SP -23.2 +/- 7.5 microEq/min; Cl- basal 21.7 +/- 7.5 to SP -16.5 +/- 5.6 microEq/min). Under basal conditions, there was minimal secretion of potassium (-0.264 +/- 0.282 microEq/min); during SP infusion, K+ flux was altered to significant secretion (-1.784 +/- 0.271 microEq/min). Serum concentrations of Na and Cl were unchanged during SP infusion, but serum potassium concentrations fell from 4.64 +/- 0.12 to 3.85 +/- 0.40 mEq/l. The data demonstrate that substance P at levels noted in the carcinoid syndrome induces significant jejunal secretion of water and electrolytes in the dog.
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PMID:Substance P-induced intestinal secretion of water and electrolytes. 242 93

The acute and chronic renal effects of indoramin, an alpha 1-adrenoceptor antagonist, were investigated in six normotensive men (mean +/- SEM age, 36 +/- 3 years). Renal clearance studies were done during steady-state water diuresis before administration of indoramin (baseline), 3-4 h after a single 50-mg oral dose (acute study), and after 7 days of treatment with 25 mg twice daily (chronic study). After a single 50-mg oral dose, mean supine blood pressure decreased from 117/76 mm Hg at baseline to 109/74 mm Hg (NS), and glomerular filtration rate and renal blood flow were unchanged. There were small decreases (0.05 less than p less than 0.1) in the fractional excretion of sodium and potassium. After chronic administration (7 days) of indoramin, no significant changes in blood pressure, renal function, renal hemodynamics, or fluid and electrolyte excretion were observed. Mean body weight tended to decrease and fractional sodium excretion increased slightly (NS) after 7 days of indoramin. Plasma renin and aldosterone concentrations tended to increase (NS) after chronic indoramin administration. The results of this study indicate that acute and chronic administration of indoramin does not adversely affect renal function, renal hemodynamics, or fluid and electrolyte excretion in normotensive subjects.
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PMID:The acute and chronic effects of indoramin on renal function, hemodynamics, and transport. 242 92

An improved sensitive assay for collagenase, which uses [3H]telopeptide-free collagen as a substrate, was used to measure changes in serum collagenase levels in 96 women and ten men (18-35 years old). Both latent and active forms of collagenase were detected in serum by molecular sieve chromatography; these forms had a relative molecular weight (Mr) of 65,000 and 45,000, respectively. Only latent collagenase was detected in crude serum after destroying inhibitors by treatment with 3 M potassium thiocyanate. Collagenase levels in males were lower than in nongravid females (34 +/- 5 versus 53 +/- 5 U/dL; mean +/- SEM; 1 unit = 1 microgram collagen digested per minute at 30C). During pregnancy there was no significant change in serum collagenase levels until the onset of spontaneous labor in full-term pregnancies (37-42 weeks), at which point there was a 66% increase over the nongravid level to a value of 88 +/- 5 U/dL. There was a further rise at one day postpartum, and high levels continued for at least four days. Women in premature labor (24-36 weeks) exhibited an eightfold increase in the level of serum collagenase to 405 +/- 110 U/dL; 16 of 17 patients in this group had collagenase levels above the 95th percentile for women at 16-40 weeks but not in labor. This evaluation of serum collagenase may provide a key for detecting premature labor. It is suggested that the increase in serum collagenase arises from the lower uterine segment and cervix.
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PMID:High levels of serum collagenase in premature labor--a potential biochemical marker. 243 51

Drusen are small, yellowish deposits that form under the retinal pigment epithelium (RPE) with senescence or under certain pathological conditions. The present study examined these structures under the scanning electron microscope. Tissue came from four eyes of 66- and 75-year-old donors who demonstrated widespread drusen of the posterior fundus noted on postmortem examination. Specimens were prepared by either detaching the RPE from Bruch's membrane, or by cryofracturing the tissue for cross-sectional views. Drusen appeared to be composed of irregularly-shaped globular masses and of distinct spherical entities. These particles varied greatly in size, and were situated between the RPE's basement membrane and the outer collagenous zone of Bruch's membrane. Surface views showed drusen components to be embedded in the collagenous zone of Bruch's membrane. Pits corresponding to the sizes of the globular and spherical masses imply that some particles were lost during tissue processing. Fractured cross sections of the irregularly-shaped globular masses revealed a homogeneous, granular matrix with no distinct ultrastructural features, while some of the fractured spherical components demonstrated an internal core. Transmission electron microscopic analysis on the same specimens that were subjected to SEM corroborated these observations. Analytical x-ray microanalysis (Kevex, Foster City, CA) in the SEM revealed major peaks for calcium and phosphorous in the crystalline spherical components, and primarily potassium and chloride in the globular structures.
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PMID:Scanning electron microscopy of human drusen. 243 70

The binding and internalization of 125I-nerve growth factor (NGF) by PC12 pheochromocytoma cells was studied as a function of extracellular potassium concentration. Both surface-bound and internalized fractions of 125I-NGF associated with the cells under depolarizing conditions (50 mM K+) increased to 144 +/- 28% (average +/- SEM, six different cell preparations) and to 176 +/- 12% (n = 6), respectively, of those observed at 6.0 mM K+. Scatchard-type analysis of the data indicates increased sites for the binding and internalization of iodinated NGF by the cells. Similar enhancement was observed for cells treated with NGF as well. This voltage-dependent phenomenon was reversible, and also observed in the presence of veratridine. Moreover, withdrawal of extracellular Ca2+ abolished high K+-induced modulation of 125I-NGF binding and internalization, indicating that this effect may be mediated by Ca2+.
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PMID:Depolarization-induced increase in surface binding and internalization of 125I-nerve growth factor by PC12 pheochromocytoma cells. 244 17

The clinical pharmacology of potassium channel openers has been reviewed using pinacidil as a prototype drug. When administered acutely or chronically, the hemodynamic and neuroendocrine profile is that of a peripheral arterial vasodilator. The drug produces decreases in peripheral vascular resistance, and subsequent blood pressure decreases are associated with reflex increments in heart rate. When studied, plasma catecholamines increased about twofold during chronic therapy. Plasma renin activity, however, was not increased during chronic therapy with pinacidil monotherapy. When patients were treated with pinacidil doses ranging from 12.5 to 75 mg b.i.d., 66.9% of patients had a decrease in supine diastolic blood pressure to below 91 mm Hg and 10 mm Hg less than baseline, whereas only 23.9% of patients had similar falls during placebo treatment. During maintenance therapy with pinacidil, the average blood pressure during the daytime dosing interval was 137.8 +/- 1.2/83.4 +/- 0.7 mm Hg (mean +/- SEM). Titration of pinacidil as monotherapy resulted in a characteristic adverse event profile dominated by the presence of dose-related edema. Other characteristic events included tachycardia, palpitations and headache. When pinacidil was given to patients unresponsive to hydrochlorothiazide (25 mg b.i.d.), similar efficacy relative to placebo was noted with a change of post-dose supine diastolic blood pressure in the pinacidil group of 13.5 +/- 0.8 mm Hg and 7.3 +/- 0.9 mm Hg in the placebo group.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Clinical pharmacology of pinacidil, a prototype for drugs that affect potassium channels. 246 78

The insulin-like growth factor-I (IGF-I) plasma concentration was evaluated as a nutritional parameter in 18 patients affected with chronic malnutrition secondary to biliopancreatic bypass and compared with albumin, transferrin, and with body composition parameters: total body water (TBW), total body sodium (TBNa), total body potassium (TBK). Subjects were studied in malnutritional conditions and after 20 to 30 days of parenteral and enteral refeeding treatment. Immunoreactive IGF-I concentration was 0.35 U/ml +/- 0.07 (mean +/- SEM), significantly lower (p less than 0.01) than in age-matched controls (1.14 +/- 0.07 U/ml, n = 29) and rose significantly (0.84 +/- 0.12 U/ml; p less than 0.01) in parallel with the improvement of nutritional status. The ratios TBNa/TBW, TBNa/TBK, and TBK/TBW were then considered as reference parameters for definition of malnutritional state, and compared with IGF-I as well as with the most commonly used parameters, albumin and transferrin. Before treatment, IGF-I evidenced higher specificity (true negative ratios 0.63, 0.43, and 0.40 with regard to TBNa/TBW, TBNa/TBK, and TBK/TBW, respectively) than albumin (0.13, 0.14, and 0.10) and transferrin (0 in all cases), and slightly less sensitivity (true positive ratios for IGF-I 0.80, 0.67, and 0.67; always one for albumin and transferrin). Moreover, IGF-I resulted definitely more sensitive in assessing the effectiveness of the refeeding treatment and, on the basis of the likelihood ratio, it appeared a good discriminator of the nutritional status. The data indicate that different nutritional factors regulate IGF-I, albumin, and transferrin, and suggest that IGF-I can be used as a reliable and specific nutritional parameter, complementary to the others currently used.
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PMID:Insulin-like growth factor-I in human malnutrition: relationship with some body composition and nutritional parameters. 250 76

There have been no detailed in-vitro studies of PRL secretion by human macroprolactinoma cells exposed to bromocriptine (BC) to within a few days of surgical removal. We have studied cells from four such tumours (serum PRL 7.05-247 U/l) and six untreated tumours (serum PRL 4-80.35 U/l) using a perifusion technique. The BC-treated tumours had shown tumour shrinkage and were treated until 40-96 h before surgery, but in one patient serum PRL had not suppressed below 15 U/l despite chronic treatment. Pretreatment serum PRL responses to TRH were blunted in all 10 patients. During perifusion with dopamine (DA, 5 mumol/l) untreated prolactinomas had a higher PRL secretion rate (19.3 +/- 2.7 microU/mg tissue/min, mean +/- SEM) than BC-treated (3.9 +/- 0.7, P = 0.005). When DA was removed, PRL secretion from untreated tumours increased to 129.7 +/- 18.7 microU/mg/min, but in three of the BC-treated, little increase occurred. In the fourth (from the patient whose serum PRL had not fully suppressed) PRL secretion increased from 4.4 to 25.6 microU/mg/min after DA withdrawal, and DA and BC dose-related inhibition of PRL was similar to that observed in untreated tumours. TRH (10 ng/ml), without DA, provoked increased PRL release from both untreated (266% basal secretion, n = 3) and BC-treated (298%, n = 3) tumours; this effect was completely inhibited by DA (5 mumol/l). The absence of hormones other than PRL following potassium (55 mmol/l) excluded contaminating normal pituitary. We conclude: (1) The effects of BC on prolactinoma PRL secretion may persist for at least 4 days; (2) partial in-vivo BC resistance can be due to factors other than DA receptor malfunction; (3) the apparent discrepancy between in-vivo and in-vitro TRH responses was consistent with the presence of increased hypothalamic DA tone in vivo; and (4) BC may have differential effects on TRH and DA-controlled PRL pools in the tumourous lactotroph.
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PMID:Perifusion studies of bromocriptine-treated and untreated macroprolactinomas: effects of dopamine, bromocriptine and TRH. 251 41

The possible presence of lithium transport beyond the proximal tubule was examined by measuring lithium excretion after administration of triamterene, a potassium-sparing diuretic, exclusively acting in the cortical collecting tubule. Eight young and healthy volunteers were studied on two occasions during maximal water diuresis. After obtaining baseline values triamterene (100 mg orally) or placebo was administered, and measurements continued for 4 hours. Creatinine clearance was used as a marker of glomerular filtration rate, and phosphate excretion was used as an additional marker of proximal sodium transport. Compared to placebo (P), triamterene (T) caused a significant increase in fractional excretion of sodium (P, 0.74 +/- 0.08%; T, 1.73 +/- 0.24%, mean +/- SEM; P less than 0.01), and lithium (P, 21.2 +/- 1.3%; T, 27.5 +/- 1.5%; P less than 0.01), whereas fractional excretion of phosphate remained unchanged (P, 9.8 +/- 1.3%; T, 9.4 +/- 1.5%; P = NS). These results indicate that lithium is transported in the cortical collecting tubule, and provide further evidence that the use of lithium as a marker of purely proximal tubular sodium transport is of limited value.
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PMID:Triamterene increases lithium excretion in healthy subjects: evidence for lithium transport in the cortical collecting tubule. 251 83


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