Normal values of the bioelectrical impedance vector in childhood and puberty

The purpose of this study was to determine the reference, bivariate, and tolerance intervals of the whole-body impedance vector in Italian children. This was a cross-sectional, multicenter study, and participants were chosen from the general school population. The impedance vector (standard, tetrapolar analysis at 50-kHz frequency) was measured in 3110 subjects, ages 2 to 15 y, and 2044 healthy children (1014 male and 1030 female) with weight and height within the 95th percentile were selected for the analysis (resistance-reactance graph method). The age-specific 95% confidence intervals of mean vectors and the 95%, 75%, and 50% tolerance intervals for individual vector measurements were plotted using resistance and reactance components standardized by the subject's height. Mean vectors from both sexes with separate 95% confidence ellipses were considered as representative of eight different age groups, from 2 to 13 y. There was a statistically significant sex effect on vector distribution from boys and girls in the age group of 14 to 15 y. The impedance vector distribution of children was also compared with healthy adult subjects (354 male and 372 female, age 15 to 85 y). There was a progressive, statistically significant vector shortening from age 2 to 15 y toward the adults' vector position. In conclusion, we established the trajectory followed by the mean impedance vector in children over ages 2 to 15 y and also obtained the reference, bivariate, and 95%, 75%, and 50% tolerance intervals of the impedance vector by age for healthy children, with which the vectors from children with altered body composition can be tested.

Correction for age of anticardiolipin antibodies cut-off points

Immunoglobulin (Ig) isotypes G, M, and A of anticardiolipin antibodies (aCL) are considered markers of antiphospholipid syndrome (APS). They were determined by ELISA in sera of 100 healthy children aged between 6 months and 16 yrs (mean 5.4 yrs +/-3.4 SD) and 100 healthy elderly subjects aged between 65 and 103 yrs (mean 84.2 yrs +/-8.1 SD). The frequency with which they were detected was compared to that in sera of 100 healthy adults aged between 21 and 47 yrs (mean 25.8 yrs +/-5.2 SD) in order to evaluate if adult aCL cut-off levels were fit for pediatric and elderly populations. The cut-off points were calculated adding 2.5 SD to the mean values and, in the adult group, the results were 11.6 GPL, 7.5 MPL, and 23.9 APL for IgG, IgM, and IgA, respectively. In the children, IgG aCL were positive in 26 cases (26%), IgM and IgA aCL in 1 case (1%) respectively. Statistical comparison of these results to those of adults showed a higher significant frequency for children IgG aCL (P = 0.0001) with the major contribution by children aged between 6 months and 5 yrs, and a lower significant frequency for children IgA aCL (P = 0.041). In elderly subjects IgG aCL were positive in 12 cases (12%), IgM aCL in 4 (4%), and IgA aCL in 37 (37%). In a comparison of these values to those of adults, only elderly IgA aCL frequency was significantly higher (P = 0.0001) with the major contribution by the oldest subgroup. In order to avoid false positive results for IgG aCL in children and for IgA aCL in elderly, as well as false negative results for IgA aCL in children, we introduced three new cut-off points: (1) 27.7 GPL for IgG aCL in children; (2) 13.8 APL for IgA aCL in children; and (3) 51.1 APL for IgA aCL in elderly subjects. These data suggest that a correction for age of aCL cut-off levels should be considered to raise specificity and sensitivity for APS in pediatric as well as in elderly populations.

Cellular hypertrophy in subcutaneous small arteries of patients with renovascular hypertension

Structural alterations of small arteries in patients with essential hypertension are characterized by inward eutrophic remodeling. However, small arteries in patients with secondary hypertension, as well as in experimental models of hypertension with high circulating renin, are characterized by inward hypertrophic remodeling, which is characterized by smooth muscle cell hypertrophy in animal models. The aim of our study was to determine whether remodeling of subcutaneous small arteries in patients with secondary forms of hypertension is associated with smooth muscle cell hypertrophy and/or alterations in the elastic modulus of the vessel wall. Fifteen patients with renovascular hypertension, 9 with primary aldosteronism, and 13 with essential hypertension and 9 normotensive subjects were included in the study. A biopsy of subcutaneous fat was taken from all subjects. Small arteries were dissected, and morphology was determined on a micromyograph. Unbiased estimates of cell volume and number were made in fixed material. From the resting tension-internal circumference relation of the small arteries, the incremental elastic modulus was calculated and plotted as a function of wall stress. Blood pressure was greater in patients with essential hypertension, renovascular hypertension, or primary aldosteronism than in normotensive subjects, but no significant difference was observed among the 3 groups of hypertensive patients. The media/lumen ratio, the medial cross-sectional area, and the smooth muscle cell volume were significantly greater in patients with renovascular hypertension than in normotensive subjects and patients with essential hypertension. No difference in cell number or in the elastic properties was observed among the 4 groups of subjects. In conclusion, our data demonstrate for the first time that a pronounced activation of the renin-angiotensin-aldosterone system is associated with vascular smooth muscle cell hypertrophy in human hypertension in a manner similar to that found in animal models.

Altered tissue electric properties in lung cancer patients as detected by bioelectric impedance vector analysis

Modifications of body composition are frequent in cancer patients. Bioelectric impedance analysis can specifically detect changes in tissue electric properties, which may be associated with outcome. We evaluated the distribution of the impedance vectors from 63 adult male patients with lung cancer, stages IIIB (33 patients) and IV (30 patients), in supportive therapy. Body weight change over the previous 6 m.o. was the same in both groups (stable/increased 36% and decreased in 62%). Patients were compared with 56 healthy subjects matched for gender, age, and body mass index (25 kg/m2). Impedance measurements (standard tetrapolar electrode placement on the hand and foot) were made with 50-kHz alternating currents. The resistance and reactance of the vector components were standardized by the height of the subjects and were plotted as resistance/reactance graphs. The impedance vector distribution was the same in patients with either stage IIIB or IV cancer. The mean vector position differed significantly between cancer patients and control subjects (Hotelling T2 test, P < 0.01) because of a reduced reactance component (i.e., a smaller phase angle) with preserved resistance component in both cancer groups. Patients with a phase angle smaller than 4.5 degrees had a significantly shorter, i.e., 18 m.o., survival. Body weight loss was not significantly associated with survival. In conclusion, impedance vectors from lung cancer patients were characterized by a reduced reactance component. The altered tissue electric properties were more predictive than weight loss of prognosis.

Relationship between central venous pressure and bioimpedance vector analysis in critically ill patients

OBJECTIVE

To assess the relationship between central venous pressure values and bioelectrical impedance vector analysis (BIVA), which may be used as complementary methods in the bedside monitoring of fluid status.

DESIGN

Cross-sectional evaluation of a consecutive sample.

SETTING

Intensive care unit of a university hospital.

PATIENTS

One hundred and twenty-one consecutive Caucasian, adult patients of either gender, for whom routine central venous pressure measurements were available.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Central venous pressure values and impedance vector components (i.e., resistance and reactance) were determined simultaneously. Total body water predictions were obtained from regression equations according to either conventional bioimpedance analysis or anthropometry (Watson and Hume formulas). Variability of total body water predictions was unacceptable for clinical purposes. Central venous pressure values significantly and inversely correlated with individual impedance vector components (r2 = .28 and r2 = .27 with resistance and reactance, respectively), and with both vector components together (R2 = .31). Patients were classified in three groups according to their central venous pressure value: low (0 to 3 mm Hg); medium (4 to 12 mm Hg); and high (13 to 20 mm Hg). Three BIVA patterns were considered: vectors within the target (reference) 75% tolerance ellipse (normal tissue hydration); long vectors out of the upper pole of the target (dehydration); and short vectors out of the lower pole of the target (fluid overload). The agreement between BIVA and central venous pressure indications was good in the high central venous pressure group (93% short vectors), moderate in the medium central venous pressure group (35% normal vectors), and poor in low central venous pressure group (10% long vectors).

CONCLUSIONS

Central venous pressure values correlated with direct impedance measurements more than with total body water predictions. Whereas central venous pressure values >12 mm Hg were associated with shorter impedance vectors in 93% of patients, indicating fluid overload, central venous pressure values <3 mm Hg were associated with long impedance vectors in only 10% of patients, indicating tissue dehydration. The combined evaluation of intensive care unit patients by BIVA and central venous pressure may be useful in therapy planning, particularly in those with low central venous pressure in whom reduced, preserved, or increased tissue fluid content can be detected by BIVA.

High-dose, not low-dose insulin increases the vasoconstrictor effect of norepinephrine in spontaneously hypertensive rats: effects of antihypertensive treatment

The effect of insulin on the vasoconstriction induced by norepinephrine is presently controversial. Therefore, the aims of our study were: (1) to evaluate the effect of low- and high-dose insulin on the concentration-response curve to norepinephrine in small resistance arteries of spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) before and after the development of hypertension, and (2) to evaluate the effects of antihypertensive treatment on vascular response to insulin and norepinephrine. Fifty-six rats were included in the study. Six SHR were treated with enalapril and 6 with candesartan cilexetil from the 4th to the 12th week of age, while 10 WKY and 14 SHR were kept untreated. Two additional groups of 10 untreated SHR and 10 WKY were killed at 4 weeks of age, in a prehypertensive phase. Mesenteric small arteries were dissected and mounted on a micromyograph. A dose-response curve to norepinephrine was performed at cumulative concentrations in the presence or absence of low- and high-dose insulin. We found that only high-dose insulin increased the vascular response to norepinephrine in 12-week-old SHR, but not in 4-week-old SHR or in age-matched WKY. The increased responsiveness to norepinephrine disappeared after preincubation of the vessels with a selective inhibitor of endothelin-1 type A receptors. After antihypertensive treatment with enalapril or candesartan cilexetil, the potentiation of the vasoconstrictor response to norepinephrine was abolished. In conclusion, insulin at high, nonphysiological doses seems to induce an increase in the reactivity to norepinephrine in mesenteric small arteries of SHR, possibly mediated by a local production of endothelin-1. Antihypertensive treatment with an ACE inhibitor or an angiotensin II receptor blocker may normalize this altered response. This mechanism may be relevant in the development of hypertension in SHR.

Platelet/polymorphonuclear leukocyte interaction: P-selectin triggers protein-tyrosine phosphorylation-dependent CD11b/CD18 adhesion: role of PSGL-1 as a signaling molecule

Polymorphonuclear leukocyte (PMN) adhesion to activated platelets is important for the recruitment of PMN at sites of vascular damage and thrombus formation. We have recently shown that binding of activated platelets to PMN in mixed cell suspensions under shear involves P-selectin and the activated beta2-integrin CD11b/CD18. Integrin activation required signaling mechanisms that were sensitive to tyrosine kinase inhibitors.1 Here we show that mixing activated, paraformaldehyde (PFA)-fixed platelets with PMNs under shear conditions leads to rapid and fully reversible tyrosine phosphorylation of a prominent protein of 110 kD (P approximately 110). Phosphorylation was both Ca2+ and Mg2+ dependent and was blocked by antibodies against P-selectin or CD11b/CD18, suggesting that both adhesion molecules need to engage with their respective ligands to trigger phosphorylation of P approximately 110. The inhibition of P approximately 110 phosphorylation by tyrosine kinase inhibitors correlates with the inhibition of platelet/PMN aggregation. Similar effects were observed when platelets were substituted by P-selectin-transfected Chinese hamster ovary (CHO-P) cells or when PMN were stimulated with P-selectin-IgG fusion protein. CHO-P/PMN mixed-cell aggregation and P-selectin-IgG-triggered PMN/PMN aggregation as well as P approximately 110 phosphorylation were all blocked by antibodies against P-selectin or CD18. In each case PMN adhesion was sensitive to the tyrosine kinase inhibitor genistein. The antibody PL-1 against P-selectin glycoprotein ligand-1 (PSGL-1) blocked platelet/PMN aggregation, indicating that PSGL-1 was the major tethering ligand for P-selectin in this experimental system. Moreover, engagement of PSGL-1 with a nonadhesion blocking antibody triggered beta2-integrin-dependent genistein-sensitive aggregation as well as tyrosine phosphorylation in PMN. This study shows that binding of P-selectin to PSGL-1 triggers tyrosine kinase-dependent mechanisms that lead to CD11b/CD18 activation in PMN. The availability of the beta2-integrin to engage with its ligands on the neighboring cells is necessary for the tyrosine phosphorylation of P approximately 110.

Effects of candesartan cilexetil and enalapril on structural alterations and endothelial function in small resistance arteries of spontaneously hypertensive rats

It was previously observed that a significant regression of structural alterations and endothelial dysfunction in mesenteric small arteries of spontaneously hypertensive rats (SHRs) may be obtained after therapy with angiotensin-converting enzyme (ACE) inhibitors. It is not clear whether angiotensin II-type 1 receptor blockers may share this properties. We evaluated the effects of the ACE inhibitor enalapril and of the angiotensin II-receptor blocker candesartan cilexetil on structural alterations of mesenteric small resistance arteries, on cardiac mass, and on endothelial function in SHRs. Seventy-three rats were included in the study. Sixteen SHRs were treated with enalapril and 21 with candesartan cilexetil, whereas 18 Wistar-Kyoto (WKY) and 18 SHRs were untreated. Enalapril and candesartan cilexetil were administered in the drinking water from weeks 4 to 12 of age. Blood pressure was measured noninvasively every week. The rats were killed at the end of the treatment period, after 3 or 4 days of therapeutic washout. Heart weight/body weight ratio (HW/BW) was measured. Mesenteric arterioles were dissected and mounted on a micromyograph (Mulvany's technique). Then the media-to-lumen ratio (M/L) was evaluated. In addition, endothelium-dependent and endothelium-independent relaxation was evaluated by dose-response curves to acetylcholine (in the presence or absence of a bradykinin-receptor blocker and of indomethacin) and sodium nitroprusside. Systolic blood pressure was significantly reduced by both drugs, compared with untreated SHRs, although the hypotensive effect was greater with enalapril than with candesartan cilexetil. A significant reduction of M/L of mesenteric small arteries and of HW/BW was observed in SHRs treated with candesartan cilexetil or enalapril. A significant improvement of endothelial function, as evaluated by a dose-response to acetylcholine, was observed. The acetylcholine-induced vasodilatation was similar after addition to the organ bath of a selective blocker of bradykinin receptors, thus suggesting a minor role (if any) of the increased local availability of bradykinin, as a consequence of inhibition of ACE, in the improvement of endothelial function observed after enalapril treatment. In addition to a satisfactory antihypertensive effect observed with both drugs, candesartan cilexetil and enalapril were proven to be equally effective in reducing structural alterations in mesenteric small resistance arteries, in normalizing cardiac mass, and in improving endothelial function. The inhibition of bradykinin breakdown does not seem to be involved in the improvement of endothelial dysfunction observed with ACE inhibitors.

Effects of hypotensive and non-hypotensive doses of manidipine on structure, responses to endothelin-1 and ICAM-1 production in mesenteric small resistance arteries of spontaneously hypertensive rats

OBJECTIVE

We have evaluated the effects of a new calcium channel blocker, manidipine, given at both high, hypotensive and low, non-hypotensive doses, on vascular morphology, response to endothelin-1 and ICAM-1 production in mesenteric small resistance arteries of spontaneously hypertensive rats (SHR).

METHODS

Ten SHR were treated with manidipine 3 mg/kg per day (high dose) and 10 with manidipine 0.3 mg/kg/per day (low dose). The drug was administered by gavage from the 4th to 12th weeks of age. Eighteen Wistar-Kyoto (WKY) rats and 18 SHR were kept untreated as controls. Rats were killed at 13 weeks. Mesenteric small arteries were dissected and mounted on a micromyograph for determination of indexes of vascular structure (media thickness, wall thickness, media/lumen ratio).

RESULTS

Systolic blood pressure was significantly reduced by the high dose of the drug, while no effect was observed with low-dose manidipine. A reduction in the media/lumen ratio was observed only in SHR treated with high-dose manidipine. The response to endothelin-1 in untreated SHR was significantly lower in comparison with WKY; a significant reduction was observed in SHR treated with high-dose manidipine. ICAM-1 vascular concentrations were higher in untreated SHR than in WKY controls. Both high- and low-dose manidipine reduced ICAM-1 concentrations toward normalization.

CONCLUSIONS

Manidipine at high, hypotensive, but not at low, non-hypotensive doses has been proven to reduce structural alterations in mesenteric small resistance arteries, and to normalize vascular responses to endothelin-1. In addition, manidipine, at both low and high doses, may reduce ICAM-1 vascular production, thus suggesting a possible anti-atherogenic effect.

Polymorphonuclear leukocytes induce PDGF release from IL-1beta-treated endothelial cells: role of adhesion molecules and serine proteases

Polymorphonuclear leukocytes (PMNs) and endothelial cells interact at sites of vascular injury during inflammatory response and during the development of atherosclerotic lesions. Such close proximity leads to the modulation of several of the biological functions of the 2 cell types. Because we have shown previously that PMNs enhance release of growth factors from resting endothelial cells, we decided to evaluate whether coincubation of PMNs with interleukin-1beta (IL-1beta)-stimulated human umbilical vein endothelial cells (HUVEC) could further modulate mitogen release from HUVEC. We found that PMN-HUVEC coincubation resulted in a 10-fold increase in mitogen release, compared with HUVEC alone (14+/-6 versus 1.3+/-0.1). When PMNs were incubated with IL-1beta-treated HUVEC, a further increase in mitogen release (up to 35-fold) was observed. The mitogenic activity was immunologically related to platelet-derived growth factor (PDGF) because the activity was abolished by an anti-PDGF antibody. PDGF-AB antigen, detected in low concentrations in conditioned medium from HUVEC alone, was increased 4-fold when IL-1beta or PMNs were incubated with HUVEC and dramatically upregulated (up to 40-fold) when PMNs were cocultured with IL-1beta-treated HUVEC. The presence of the protease inhibitor eglin C abolished mitogenic activity generation, suggesting a role for PMN-derived elastase and cathepsin G. Indeed, purified elastase and cathepsin G mimicked PMN-induced mitogen release from HUVEC. Because PMNs firmly adhered to IL-1beta-treated HUVEC, we investigated the role of cell-cell adhesion in mitogen release. Adhesion and PDGF release were inhibited by approximately 60% in the presence of anti-CD11a/CD18 and anti-intercellular adhesion molecule-1 monoclonal antibodies. This study suggests a new role for PMNs and their interaction with endothelium in pathological conditions in which intimal hyperplasia is a common feature.

Effects of losartan and enalapril on small artery structure in hypertensive rats

We evaluated the effects on cardiovascular structure of the angiotensin-converting enzyme (ACE) inhibitor enalapril and of the angiotensin II receptor blocker losartan, administered either at hypotensive or nonhypotensive dosage in spontaneously hypertensive rats (SHR). SHR were treated from ages 4 to 12 weeks with low-dose (1 mg x kg(-1) x d(-1)) enalapril, low-dose (0.5 mg x kg(-1) x d(-1)) losartan, high-dose (25 mg x kg(-1) x d(-1)) enalapril, or high-dose (15 mg x kg(-1) x d(-1)) losartan. Untreated WKY and SHR were also studied. Rats were killed at 13 weeks of age, and the heart was weighed. Mesenteric small arteries were dissected and mounted on a micromyograph for determination of media thickness and lumen diameter. In fixed arteries, cell volume, number of cells per segment length, and number of cell layers were measured using the unbiased "disector" method. Systolic blood pressure was significantly reduced by the high doses of both drugs, but the hypotensive effect was greater with enalapril than with losartan (P<0.05). In the high-dose enalapril and losartan groups, there were similar reductions in relative left ventricular mass, media/lumen ratio, and number of cell layers of resistance arteries; however, there were no differences in the cell volume or number of cells per segment length of resistance arteries. Low-dose enalapril did not affect systolic blood pressure or any of the structural parameters. The results show that the hypotensive effects of both losartan and enalapril were associated with outward remodeling of resistance arteries at the cellular level. The effect of losartan on resistance artery structure was equal to that of enalapril, despite the smaller hypotensive effect.

Bone metabolism in orthotopic liver transplantation: a prospective study

Bone mineral density (BMD) and mineral metabolism were assessed in 54 patients with end-stage liver disease who were evaluated for orthotopic liver transplantation (OLT) and assessed 3, 6, and 12 months after surgery in 26 patients who underwent OLT. Serum and urinary electrolyte and mineral levels, serum liver function test results, and parathyroid hormone (PTH), osteocalcin (BGP), 25-hydroxyvitamin D, and urinary hydroxyproline levels were assessed. BMD of the lumbar spine was measured at baseline and 3, 6, and 12 months after OLT. At baseline, 40.7% of patients had BMD below the fracture threshold (0.800 g/cm2). Using multiple stepwise regression analysis, we found that BMD was significantly (P < .0001) affected by age, serum creatinine level, and PTH level but not by indices of cholestasis or liver function. In the patients who underwent OLT, a 1.4% reduction (P < .006) was observed in BMD 3 months after OLT. Thereafter, BMD returned to pretransplant values. A significant increase in serum BGP was observed after 6 (P < .02) and 12 (P < . 005) months. PTH levels increased progressively 3 (P < .02), 6 (P < . 001), and 12 (P < .0001) months after OLT. This increase did not seem to be caused by cyclosporine-induced nephropathy. It was concluded that osteopenia is a major complication in hepatic cirrhosis, regardless of its causes. The increase in serum BGP levels 6 and 12 months after OLT indicates metabolic activation of osteoblasts. The increase in PTH levels after OLT warrants further investigation.

Identification of operational clues to dry weight prescription in hemodialysis using bioimpedance vector analysis. The Italian Hemodialysis-Bioelectrical Impedance Analysis (HD-BIA) Study Group

In patients undergoing hemodialysis (HD) cyclic body fluid changes are estimated by body weight variations, which may be misleading. Conventional bioelectrical impedance analysis (BIA) produces biased estimates of fluids in HD due to the assumption of constant tissue hydration. We used an assumption-free assessment of hydration based on direct measurements of the impedance vector. The impedance vector (standard BIA at 50 kHz frequency) was measured in 1367 HD patients, ages 16 to 89 years with BMI 17 to 31 kg/m2, 1116 asymptomatic (680 M and 436 F), and 251 with recurrent HD hypotension (118 M and 133 F) before and after two HD sessions (thrice weekly bicarbonate dialysis, 210 to 240 min) removing 2.7 kg fluid. The vector distribution of HD patients was compared to 726 healthy subjects with the same age and BMI range. Individual vector measurements (resistance and reactance components) were plotted on the gender specific 50th, 75th and 95th percentiles of the vector distribution in the healthy population (reference tolerance ellipses) as a resistance-reactance graph (RXc graph). The wet-dry weight cycling of HD patients was represented on the resistance-reactance plane with a definite, cyclical, backward-forward displacement of the impedance vector. The vectors of patients with HD hypotension were less steep and more often shifted to the right, out of the reference 75% tolerance ellipse, than asymptomatic patients. A wet-dry weight prescription, based on BIA indications, would bring the vectors of patients back into the 75% reference ellipse, where tissue electrical conductivity is restored. Whether HD patients with vector cycling within the normal third quartile ellipse have better outcome awaits confirmation by longitudinal evaluation.

Discriminating between body fat and fluid changes in the obese adult using bioimpedance vector analysis

OBJECTIVE

Conventional body composition methods may produce biased quantification of fat and fat-free mass in obese subjects, due to possible violation of the assumption of constant (73%) tissue hydration. We used an assumption-free, graphical method for interpreting body weight variation in obesity using bioelectrical measurements.

DESIGN

540 obese subjects with body mass index (BMI) > 31 kg/m2 without apparent edema were compared to 726 healthy subjects with BMI < 31 kg/m2 and to 50 renal patients with apparent edema. A subgroup of 48 obese subjects were evaluated again after weight loss (8.6 kg, 3 BMI units) following one-month energy restriction (5 MJ/d, 1200 kcal/d). 32 obese uremic patients were evaluated before and after a dialysis session (3.2 kg fluid removed). Direct measurements obtained from standard 50 kHz frequency bioelectrical impedance analyzer were used as impedance vectors in the Resistance-Reactance Graph.

RESULTS

1) Impedance vectors of obese subjects could be discriminated from those of edematous patients with 91% correct allocation; 2) A significant lengthening of vectors was observed after fluid loss of 3 kg in obese subjects; but 3) A body weight loss of about 9 kg after energy restriction was associated with no vector displacement.

CONCLUSION

A different impedance vector pattern was associated with body weight loss in obesity due to fluid removal (vector lengthening) versus an energy-restricted diet (no vector displacement).

The vasoconstriction induced by endothelin-1 is mediated only by ET(A) receptors in mesenteric small resistance arteries of spontaneously hypertensive rats and Wistar Kyoto rats

OBJECTIVE

To evaluate the functional responses of mesenteric small resistance arteries of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rat controls to endothelin-1 (ET-1), in the presence and absence of an ET(A) receptor antagonist drug as well as to an ET(B) receptor agonist.

METHODS

Twenty rats aged 12 weeks were studied. They were 10 SHR and 10 WKY rats. Mesenteric small resistance arteries (relaxed diameter 100-180 microm) were dissected and mounted on a micromyograph (Mulvany's technique). A dose-response curve for response to ET-1 was plotted for cumulative concentrations (from 10(-11) to 10(-8) mol/l) in the presence and absence of 10(-6) mol/l FR 139317 (a selective antagonist of ET(A) receptors). In addition, the effects of 10(-7) mol/l N-succinyl-[Glu9, Ala11,15]-endothelin 1 fragment 8-21 (IRL 1620, a selective agonist of ET(B) receptors) were evaluated.

RESULTS

The response of ET-1 was greater in WKY rats than it was in SHR. Almost all the vasoconstrictor effect of ET-1 could be prevented by addition of FR 139317, whereas the agonist of ET(B) receptors had no effect (no change in active force).

CONCLUSIONS

The contractile effects of ET-1 on mesenteric small resistance arteries of SHR and WKY rats are mediated mostly by ET(A) receptors, whereas ET(B) receptors play a minor role, if any. It is possible, however, that a vasoconstrictor effect of ET(B) receptors on the smooth muscle could be masked by the concomitant stimulation of endothelial ET(B) vasodilator receptors.

Prediction of the Third and Fourth Heart Sounds by Doppler Echocardiography

Doppler echocardiographic variables were sought for predicting the third and fourth heart sounds, as documented by phonocardiography. Phonocardiographic recordings of gallop sounds and Doppler echocardiographic investigations of mitral inflow and pulmonary venous flow were evaluated in 85 subjects by discriminant and multiple regression analysis. Of 85 subjects 47% had a third sound and 72% a fourth sound, evaluated by phonocardiography. A correct identification of 85% subjects with, and 82% without, the third sound was possible by discriminant analysis using the ratio of peak early diastolic to peak atrial mitral flow velocity (FV), the interval from peak ECG R wave to peak early diastolic mitral FV, and the early diastolic mitral FV deceleration time. At the observed prevalence of the third heart sound (47%), the predictive positive value was 81% and the predictive negative value was 86%. A correct identification of 72% of the subjects with, and 83% without, a fourth sound was possible by discriminant analysis using the ratio of peak early diastolic to peak atrial mitral FV, the interval between the end of atrial mitral FV and the peak ECG R wave, and the duration of pulmonary venous reverse FV at atrial systole. At the observed prevalence of the fourth heart sound (72%) the predictive positive value was 92% and the predictive negative value was 54%. By multiple regression analysis, up to 50% of the amplitude of both gallop sounds was predictable by a combination of Doppler echocardiographic variables.

Isolation and characterization of a digoxin-like immunoreactive substance from human urine by affinity chromatography

A series of observations has suggested that one or more digoxin-like immunoreactive substances (DLIS) in biological fluids is able to cross-react with the antidigoxin antibody. Whether this substance is the endogenous inhibitor of Na+/K+ ATPase has not been well established. The aim of this study was to identify and characterize DLIS from human urine. Treated urine from healthy men was run on an affinity chromatography column at a flow rate of 1 mL/min in which the ligand was an antibody (antiserum) to digoxin. Eluates from affinity chromatography were applied onto analytical reversed-phase HPLC. The active material was eluted with a linear gradient of acetonitrile (from 350 to 650 mL/L) and water. A second step in HPLC was carried out isocratically with 280 mL/L acetonitrile in water. We found a single peak showing cross-reactivity with antidigoxin antibody as measured by RIA. It showed the same retention time as that of a digoxin calibrator. This highly purified substance is able to displace [3H]ouabain from dog kidney-derived Na+/K+ ATPase, to inhibit Na+/K+ ATPase activity as measured by the 86Rb+ uptake in red blood cells and by coupled enzyme assay. Our results are consistent with the hypothesis that DLIS, as isolated by this particular digoxin antibody, is a single substance and an inhibitor of Na+/K+ ATPase.

Asymmetry of the total body water prediction bias using the impedance index

Our purpose was to prove on a geometric basis that the bias of total body water (TBW) prediction equations based on the impedance index is far greater in fluid overloading than in dehydration. We used formal evaluation of conventional bioimpedance regression equations in both normal and abnormal body fluid status. We plotted the hyperboloid function generated from a standard prediction equation for the TBW over the resistance-reactance (RXc) plane containing the bivariate tolerance intervals (ellipses) of the healthy population. The equation estimated 35 L TBW for the average man (both sexes) of 170 cm height. Leaving the center of the tolerance ellipses, over which the function was relatively flat, the predicted TBW rapidly increased to absurd values for the shorter vectors, indicating fluid overloading (e.g., > 100 L for R < 170 ohm). Migration of the longer impedance vectors beyond the upper pole of 95% tolerance ellipse, which is in the dehydration region, produced less biased estimates of TBW (e.g., < 22 L for the extreme R values > 850 ohm). Different formulas produced TBW prediction bias of the same order. Due to the hyperbolic shape, functions of the impedance index are critically dependent on the region of the RXc plane where they are calculated and they produce misleading results in patients with fluid overload.

Recurrence after resection for ductal adenocarcinoma of the pancreas

We analyzed the pattern of failure and clinicopathologic factors influencing the disease-free survival of 78 patients who died after macroscopic curative resection for pancreatic cancer. Local recurrence was a component of failure in 56 patients (71.8%) and hepatic recurrence in 48 (61.5%), both accounting for 97% of the total recurrence rate. About 95% of recurrences occurred by 24 months after operation. Median disease-free survival time was 8 months, and cumulative 1-, 3-, and 5-year actuarial disease-free survival rates were 66%, 7%, and 3%, respectively. Multivariate analysis showed that tumor grade (p = 0.04), microscopic radicality of resection (p = 0.04), lymph node status (p = 0.01), and size of the tumor (p = 0.005) were independent predictors of disease-free survival. Patterns of failure and disease-free survival were not statistically influenced by the type of surgical procedure performed. Median survival time from the detection of recurrence until death was 7 months for local recurrence versus 3 months for hepatic or local plus hepatic recurrence (p < 0.05). From our experience and the data collected from the literature, it appears that surgery alone is an inadequate treatment for cure in patients with pancreatic carcinoma. Effective adjuvant therapies are needed to improve locoregional control of pancreatic cancer after surgical resection.

A new method for monitoring hydration at high altitude by bioimpedance analysis

Our study evaluated the performance of a graphical method for monitoring the fluid variation at high altitude in seven adult Caucasian male subjects (average age 25 yr, average height 177 cm). The graphical approach is called the Resistance-Reactance (RXc) graph method and is based on standard bioimpedance analysis (tetrapolar, 50 kHz frequency). Measurements were taken at sea level before the expedition, at 5050 m after 1 wk and 3 wk, and again at sea level after descent. Plasma and urine electrolytes, osmolalities, and the free-water clearance were determined by standard methods. All climbers had baseline impedance vectors within the reference 95% tolerance ellipse for the Italian male population. The high altitude dehydration caused a significant lengthening of vectors, which after descent underwent a significant shortening and returned close to the baseline values. Average urine volume increased by 1.4 l.d-1 in the first week and average body weight decreased by 4.4 kg after 3 wk. The RXc graph method could be useful in the planning of the individual climber's appropriate dehydration and fluid intake at altitude since a feedback control of the hydration is allowed without any assumption of body composition.

Thrombin-activated human platelets release two NAP-2 variants that stimulate polymorphonuclear leukocytes

Thrombin-activated human platelets release substance(s) of a proteic nature which induce an increase in the intracellular calcium concentration in polymorphonuclear leukocytes (PMN). Aim of this study was to characterize the platelet released product(s) responsible for PMN stimulation. PMN-stimulating activity was isolated from platelet supernatant by FPLC and HPLC. The N-terminal sequence analysis revealed that the purified fractions consisted in 90% of a peptide of 73 amino acids and in 10% of a peptide of 74 amino acids; both are truncated forms of the connective tissue-activating peptide III (CTAP-III), a platelet alpha-granule product, and have 3 and 4 additional amino acids at the N-terminus compared with the neutrophil-activating peptide 2 (NAP-2): Asp-Leu-Tyr and Ser-Asp-Leu-Tyr, respectively. Treatment of platelet supernatant (previously depleted of PMN-activating nucleotides) with Affi-gel heparin resulted in the disappearance of PMN-stimulating effects, suggesting that NAP-2 variants, which are heparin-binding proteins, account for ATP-independent PMN-stimulating activity of the supernatant. Cross-desensitization between rNAP-2 and the platelet supernatant and inhibition by the anti-NAP-2 antibody are in agreement with this conclusion. Although NAP-2 and its variants are reportedly generated from the inactive precursors, CTAP-III and platelet basic protein, through a proteolytic cleavage, NAP-2 variants were not generated in our system by proteases deriving from platelets or contaminating leukocytes. Indeed, treatment of intact platelet suspensions with different protease inhibitors failed to modify the calcium stimulating activity of the resulting supernatants. In conclusion, thrombin-activated platelets release NAP-2 variants which are not generated outside the platelets by proteolytic processing but are released in an active form. This finding enhances our understanding of platelet-PMN interaction in thrombosis and inflammation.