Individual differences in paired comparison data.

Thurstonian models provide a flexible framework for the analysis of multiple paired comparison judgments because they allow a wide range of hypotheses about the judgments' mean and covariance structures to be tested. However, applications have been limited to a large extent by the computational intractability involved in fitting this class of models. This paper demonstrates that the Monte Carlo EM algorithm facilitates maximum likelihood estimation of Thurstonian paired comparison models even when the number of items is large. A paired comparison study is presented in detail to illustrate the estimation approach.

Testing Thurstonian Case V ranking models using posterior predictive checks.

This paper presents the results of a Monte Carlo study which investigates the validity of the method of posterior predictive checks (PPC) for testing the fit of a Thurstonian Case V ranking model. The PPC method is employed as an alternative to standard goodness-of-fit tests which are of limited use even when the number of items to be ranked is small. Several test quantities are formed to assess the fit of the Case V ranking model to data for various sample sizes and for two types of violations of the Case V assumptions: heterogeneous stimulus variances and rankers from different populations. The study concludes that the PPC method is useful in detecting local and global misfits of a Thurstonian Case V model, even when the ranking data are sparse.

Phylogenetic structure in the grass family (Poaceae): evidence from the nuclear gene phytochrome B.

Phylogenetic analyses of partial phytochrome B (PHYB) nuclear DNA sequences provide unambiguous resolution of evolutionary relationships within Poaceae. Analysis of PHYB nucleotides from 51 taxa representing seven traditionally recognized subfamilies clearly distinguishes three early-diverging herbaceous "bambusoid" lineages. First and most basal are Anomochloa and Streptochaeta, second is Pharus, and third is Puelia. The remaining grasses occur in two principal, highly supported clades. The first comprises bambusoid, oryzoid, and pooid genera (the BOP clade); the second comprises panicoid, arundinoid, chloridoid, and centothecoid genera (the PACC clade). The PHYB phylogeny is the first nuclear gene tree to address comprehensively phylogenetic relationships among grasses. It corroborates several inferences made from chloroplast gene trees, including the PACC clade, and the basal position of the herbaceous bamboos Anomochloa, Streptochaeta, and Pharus. However, the clear resolution of the sister group relationship among bambusoids, oryzoids, and pooids in the PHYB tree is novel; the relationship is only weakly supported in ndhF trees and is nonexistent in rbcL and plastid restriction site trees. Nuclear PHYB data support Anomochlooideae, Pharoideae, Pooideae sensu lato, Oryzoideae, Panicoideae, and Chloridoideae, and concur in the polyphyly of both Arundinoideae and Bambusoideae.

cDNA cloning of a myosin heavy chain isoform in embryonic smooth muscle and its expression during vascular development and in arteriosclerosis.

Adult rabbit smooth muscles contain two types of myosin heavy chain (MHC) isoforms, SM1 and SM2 which are generated through alternative RNA splicing from a single gene (Nagai, R., Kuro-o, M., Babij, P. & Periasamy, M. (1989) J. Biol. Chem. 264, 9734-9737). We previously reported that the expression of SM1 and SM2 during vascular development is differentially regulated at the level of RNA splicing, whereby SM1 is constitutively expressed from early development but SM2 appear after birth (Kuro-o, M., Nagai, R., Tsuchimochi, H., Katoh, H., Yazaki, Y., Ohkubo, A. & Takaku, F. (1989) J. Biol. Chem. 264, 18272-18275). We also demonstrated that embryonic vascular smooth muscles contain a third type of MHC isoform, referred to as SMemb in this report, which comigrates on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with SM2. In the present study we have isolated and characterized a cDNA clone (FSMHC34) for SMemb. FSMHC34 encodes the light meromyosin region including the carboxyl terminus and showed 70% amino acid sequence identity with SM1 or SM2. SMemb is a nonmuscle-type MHC and identical with brain MHC, but clearly distinct from 196-kDa nonmuscle MHC in cultured smooth muscle cells. The expression of SMemb was predominant in embryonic and perinatal aortas, but down-regulated with vascular development. Interestingly SMemb was reexpressed in proliferating smooth muscle cells of arteriosclerotic neointimas. These results suggest that smooth muscle proliferation is coupled to the expression of SMemb and that dedifferentiation of smooth muscles toward the embryonic phenotype is involved in the mechanisms underlying atherosclerosis.

Role of atrial natriuretic peptide in hemoconcentration during exercise.

Changes in plasma levels of atrial natriuretic peptide (ANP) and albumin, and blood hematocrit (Hct) during treadmill exercise were studied in 6 healthy men before and after beta-adrenergic blockade. Plasma ANP levels increased during exercise and then gradually decreased. There was a concomitant increase in both Hct and plasma albumin concentrations. Prior administration of a long-acting propranolol, 160 mg daily for 3 consecutive days, markedly elevated plasma ANP levels before, during and after exercise. In addition, the mean basal Hct increased significantly and further rose during exercise after propranolol administration. When increments in plasma ANP concentrations during exercise in individual subjects were compared with those in Hct, there was a significant positive correlation between the two variables before and after propranolol administration. The results indicate a close relationship between the changes in plasma ANP and those in Hct during exercise at different ANP levels, and suggest that ANP may be at least one of the factors involved in the hemoconcentration associated with exercise.

Atrial natriuretic peptide and vasopressin during percutaneous transvenous mitral valvuloplasty and relation to renin-angiotensin-aldosterone system and renal function.

To study the relation between plasma atrial natriuretic peptide (ANP) and cardiac pressure, and to assess the pathophysiologic significance of ANP in water and electrolyte metabolism, the changes in plasma levels of ANP and arginine vasopressin (AVP) were examined in 11 patients with mitral stenosis who underwent percutaneous transvenous mitral valvuloplasty, and compared with the changes in the renin-angiotensin-aldosterone system and renal function. Immediately after valvuloplasty, plasma ANP levels decreased significantly with a concomitant decrease in mean pressures in the left atrium, the pulmonary artery and the right atrium. Plasma ANP levels decreased to the normal range in 4 of the 6 patients with normal sinus rhythm, while all 5 patients with atrial fibrillation had higher levels despite a similar degree of decrease in atrial pressure. There were significant positive correlations between plasma ANP levels and the mean left atrial pressure (r = 0.61, p less than 0.01), the mean pulmonary arterial pressure (r = 0.49, p less than 0.01) and the mean right atrial pressure (r = 0.54, p less than 0.01). The mean plasma AVP levels, on the other hand, showed a transient increase after valvuloplasty from 0.5 +/- 0.1 to 1.2 +/- 0.4 pg/ml (p less than 0.05). The mean plasma renin activity (1.3 +/- 0.3 vs 2.7 +/- 0.8 ng/ml/hr, p less than 0.05) and plasma aldosterone concentration (8.6 +/- 2.3 vs 17.2 +/- 5.2 ng/dl, p less than 0.05) also increased significantly 30 minutes after valvuloplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid fall in elevated plasma atrial natriuretic peptide levels after successful catheter balloon valvuloplasty of mitral stenosis.

To determine whether an acute fall in atrial pressure decreases the secretion of atrial natriuretic peptide in man, changes in the plasma levels of this peptide were studied after catheter balloon valvuloplasty of the mitral valve. Ten patients with severe mitral stenosis were included in the study. The valvuloplasty resulted in an immediate reduction in left atrial pressure and an increase in the mitral valve area. Decreases in right atrial pressure were inconsistent and less significant. Plasma atrial natriuretic peptide levels, which were elevated before the valvuloplasty, decreased significantly in all 10 patients at 15 minutes after the valvuloplasty and reached lower plateaus at 30, 45, and 60 minutes after the procedure. In the seven patients studied for a longer period, both plasma atrial natriuretic peptide levels and the left atrial pressure remained reduced 24 hours after the valvuloplasty. Plasma atrial natriuretic peptide levels before and 30 to 60 minutes after the valvuloplasty were positively correlated to simultaneously determined left and right atrial pressures. These results indicate that atrial stretch caused by increased atrial pressure is an important stimulus for atrial natriuretic peptide release in man. "De-stretching" of the myocytes of the atria results in rapid inhibition of atrial natriuretic peptide secretion.

Atrial natriuretic peptide during supraventricular tachycardia and relation to hemodynamic changes and renal function.

Changes in plasma levels of atrial natriuretic peptide (ANP) and arginine vasopressin were studied in 5 patients during and after a 30-minute period of induced supraventricular tachycardia (SVT). Immediately after the induction of SVT, plasma ANP levels began to increase, peaked at 32 minutes (+734% increase on average) and then gradually decreased. The mean plasma arginine vasopressin levels decreased during SVT, but the differences were not significant. When plasma ANP levels during SVT were compared with the simultaneously measured hemodynamic variables, a significant positive correlation (r = 0.73, p less than 0.001) was observed between plasma ANP levels and pulmonary capillary wedge pressure. Induced SVT was associated with increased urinary sodium and potassium excretion, increased urine flow and increased free water clearance. Concomitantly, glomerular filtration rate significantly increased (+77%) with an increase in filtration fraction. Although no significant change was observed in plasma renin activity, plasma aldosterone concentrations decreased during and after SVT. These results suggest that increased left atrial pressure stimulates ANP release during SVT and that increased glomerular filtration rate and decreased aldosterone secretion by ANP, in addition to the inhibition of water reabsorption by decreased arginine vasopressin, may be responsible for natriuresis and diuresis associated with SVT.

Effect of beta-adrenergic blockade on plasma levels of atrial natriuretic peptide during exercise in humans.

Effect of beta-adrenergic blockade on plasma levels of atrial natriuretic peptide (ANP) during treadmill exercise was studied in 9 healthy volunteers. Plasma ANP levels increased during exercise. The mean plasma ANP concentration on 12-min exercise (32.5 +/- 3.7 pg/ml, mean +/- SEM) was significantly higher than the control (16.7 +/- 1.0 pg/ml). After exercise, the levels decreased and the mean plasma ANP concentrations in the recovery period were higher in subjects in the sitting position than in subjects who kept standing. Prior administration of a long-acting propranolol, 160 mg daily for 3 consecutive days, augmented ANP release during exercise. The mean plasma ANP concentrations on 9- and 12-min exercise (34.5 +/- 3.1 and 64.9 +/- 15.0 pg/ml, respectively) were significantly higher than those in the corresponding exercise stage without propranolol. Plasma ANP levels in the recovery period also increased after the administration of propranolol and the subjects in the sitting position again had higher plasma levels than those in the standing position. These results suggest that increased central blood volume during exercise elevates atrial pressure to stimulate ANP secretion, and that greater atrial distension and pressure due to reduced ventricular contractility by beta-adrenergic blockade facilitates ANP release to a greater extent.

Pressor response to vasopressin and norepinephrine in DOC-salt hypertensive and prehypertensive rats.

Pressor responses to arginine-vasopressin (AVP) and norepinephrine (NE) were studied in deoxycorticosterone (DOC)-salt hypertensive and prehypertensive rats. DOC-salt rats received weekly subcutaneous injection of DOC acetate (30 mg/kg) and given 1% saline for drinking. Salt and control rats received injections of sesame oil and given 1% saline or tap water, respectively. On the 5th day (prehypertensive stage) and at 6th week (hypertensive stage) after treatment had started, pressor responses were studied by measuring changes in mean arterial pressure recorded from the iliac artery in response to i.v. injections of AVP or NE under urethane anesthesia. Pressor response to AVP was enhanced both in DOC-salt hypertensive and prehypertensive rats compared with that in salt and control rats. Pressor response to NE tended to be enhanced in DOC-salt hypertensive rats, however, the enhancement was not observed in the rats in prehypertensive stage. Enhanced pressor response to AVP in DOC-salt prehypertensive rats was not due to the structural change of vascular beds, because peripheral resistance in isolated hindlimb preparations was similar in the three groups. Thus, pressor response to AVP was enhanced even in the prehypertensive stage in DOC-salt rats and the enhancement might be involved in the pathogenesis of hypertension in DOC-salt rats.

Mechanism of polyuria and natriuresis associated with paroxysmal supraventricular tachycardia.

Changes in plasma levels of atrial natriuretic peptide (ANP) and arginine vasopressin (AVP) were studied in 8 patients during a 30 min period of induced supraventricular tachycardia (SVT). The mean plasma ANP concentration increased immediately after the onset of SVT, peaked at 30 min and gradually returned to the control level. The mean plasma AVP concentration, on the other hand, was suppressed during SVT and rebounded above the control level in the post-SVT period. In 4 patients, SVT was associated with polyuria and natriuresis. The mean urine volume in these patients increased to 580% of the control and the mean urinary sodium excretion to 278% of the control, respectively. It was concluded that both a stimulation of ANP secretion and an inhibition of AVP release, elicited by an increase in atrial pressure, may be responsible for polyuria and natriuresis associated with SVT.

Dietary cellulose, zinc and copper: effects on tissue levels of trace minerals in the rat.

This study was designed to examine the effect of graded levels of cellulose, zinc and copper on tissue mineral levels. Tissue mineral levels were assayed by atomic absorption spectrophotometry in samples collected from a study which involved 12 treatments in a 3 X 2 X 2 factorial arrangement. This study involved three levels of cellulose (0, 8, and 16% of the diet), two levels of Cu (deficient and adequate; 2 and 18 mg/kg of diet, respectively), and two levels of Zn (marginal and abundant; 10 and 120 mg/kg of diet, respectively). Six weanling, male Sprague-Dawley rats were assigned to each treatment and after 9 weeks they were killed. Reductions of tissue Cu content were observed in the serum, liver, tibia and testis of the rats fed the Cu-deficient diets. The Fe content of the tibia and testis was reduced, but that of liver was elevated in the rats fed Cu-deficient diets. Reductions in tibial Zn levels were observed in the rats fed marginal-Zn as compared to those fed the abundant-Zn diets; and in the rats fed Cu-adequate as compared to those fed Cu-deficient diets. Increases in cellulose resulted in increased liver and testicular Cu content only in rats fed the Cu-deficient diets. Additions of cellulose appeared to have no adverse effect on the distribution of Zn, Cu and Fe in tissues which are sensitive to dietary deficiencies. With the exception of rats fed the copper-deficient, marginal zinc diets, the rats fed the other diets demonstrated a small reduction in serum zinc values as cellulose was increased.