Staphylococcus pseudintermedius biofilms secrete factors that induce inflammatory reactions in vitro.

Biofilms, composed of bacterial cells embedded in a secreted polysaccharide and protein matrix, often cause problems such as chronic and refractory infections. Staphylococcus pseudintermedius, which is an important pathogen in veterinary medicine, has a high rate of biofilm production. Although it is considered that S. pseudintermedius biofilms are associated with prolonged inflammatory disorders, there are no reports that S. pseudintermedius biofilm directly regulates inflammatory reactions. In this study, we focused on the metabolites derived from biofilm cultures of S. pseudintermedius and evaluated their inflammatory effects in vitro. Expression levels of interleukin-1 beta and interleukin-6 mRNA significantly increased in RAW264.7 cells that were cultured with biofilm-conditioned medium (BCM). The secreted proteins in BCM were heat resistance and activated a Toll-like receptor (TLR) signalling pathway. Moreover, based on SDS-PAGE analysis, isolates with stronger biofilm-forming capabilities induced more inflammatory reactions and had specific banding patterns compared with those of weak biofilm producers. Collectively, our results suggest that the proteins derived from S. pseudintermedius biofilm induce a host inflammatory response via a TLR pathway. Furthermore, the severity of inflammation depends on the biofilm formation capacity of the S. pseudintermedius strain. SIGNIFICANCE AND IMPACT OF THE STUDY: Staphylococcus pseudintermedius is a biofilm-forming bacterium. We identified some biofilm secreted heat-resistant proteins that induce inflammatory reactions through Toll-like receptor signalling. The expression of the secreted protein varied depending on the potency of biofilm production. Our data suggest that these proteins may be the factors causing biofilm-related inflammation during S. pseudintermedius infections. Identification of these proteins may lead to the development of novel medications to prevent the exacerbation of infections caused by S. pseudintermedius.

Strong plastic responses in aerenchyma formation in F1 hybrids of Imperata cylindrica under different soil moisture conditions.

Hybrids can express traits plastically, enabling them to occupy environments that differ from parental environments. However, there is insufficient evidence demonstrating how phenotypic plasticity in specific traits mediates hybrid performance. Two parental ecotypes of Imperata cylindrica produce F1 hybrids. The E-type in wet habitats has larger internal aerenchyma than the C-type in dry habitats. This study evaluated relationships between habitat utilisation, aerenchyma plasticity, and growth of I. cylindrica accessions. We hypothesize that plasticity in expressing parental traits explains hybrid establishment in habitats with various soil moisture conditions. Aerenchyma formation was examined in the leaf midribs, rhizomes and roots of two parental ecotypes and their F1 hybrids in their natural habitats. In common garden experiments, we examined plastic aerenchyma formation in leaf midribs, rhizomes and roots of natural and artificial F1 hybrids and parental ecotypes and quantified vegetative growth performance. In the natural habitats where soil moisture content varied widely, the F1 hybrids showed larger variation in aerenchyma formation in rhizomes than their parental ecotypes. In the common garden experiments, F1 hybrids showed high plasticity of aerenchyma formation in rhizomes, and their growth was similar to that of C-type and E-type under drained and flooded conditions, respectively. The results demonstrate that F1 hybrids of I. cylindrica exhibit plasticity in aerenchyma development in response to varying local soil moisture content. This characteristic allows the hybrids to thrive in diverse soil moisture conditions.

Vasodilator and constrictor actions of platelet-activating factor in the isolated microperfused afferent arteriole of the rabbit kidney. Role of endothelium-derived relaxing factor/nitric oxide and cyclooxygenase products.

It has been suggested that platelet-activating factor (PAF) plays a prominent role in the control of glomerular hemodynamics in various physiological and pathological conditions. We examined the direct effect of PAF on rabbit glomerular afferent arterioles (Af-Arts) microperfused in vitro and tested whether endothelium-derived relaxing factor/nitric oxide (EDNO) and cyclooxygenase products are involved in its actions. In nanomolar concentrations PAF caused dose-dependent constriction of Af-Arts, with the maximum constriction being 34 +/- 10% at 4 x 10(-8) M (n = 9, P < 0.001). The constriction was blunted by cyclooxygenase inhibition (11 +/- 6%, n = 7, P < 0.05) but augmented by EDNO inhibition (76 +/- 14%, n = 8, P < 0.005). To study a possible vasodilator effect of PAF, Af-Arts were preconstricted with norepinephrine and increasing concentrations of PAF added to the lumen. At picomolar concentrations (lower than those that caused constriction), PAF produced dose-dependent vasodilation that was unaffected by cyclooxygenase inhibition but was abolished by EDNO synthesis inhibition. Both PAF-induced constriction and dilation of Af-Arts were blocked by a PAF receptor antagonist. This study demonstrates that PAF has a receptor-mediated biphasic effect on rabbit Af-Arts, dilating them at low concentrations while constricting them at higher concentrations. Our results suggest that PAF's vasodilator action may be due to production of EDNO, while its constrictor action is mediated at least in part through cyclooxygenase products.

Endothelium-derived relaxing factor/nitric oxide modulates angiotensin II action in the isolated microperfused rabbit afferent but not efferent arteriole.

It has been reported that sensitivity to angiotensin II (Ang II) is higher in efferent (Ef) than afferent (Af) arterioles (Arts). We tested the hypothesis that this is due to arteriolar differences in the interaction between Ang II and endothelium-derived relaxing factor/nitric oxide (EDNO). Rabbit Af-Arts with glomerulus intact were microperfused in vitro at a constant pressure. Ef-Arts were perfused from the distal end of either the Af-Art (orthograde perfusion) or the Ef-Art (retrograde perfusion) to eliminate influences of the Af-Art or glomerulus, respectively. Ang II did not alter Af-Art luminal diameter until the concentration reached 10(-9) M, which decreased the diameter by 11 +/- 2.6% (n = 11; P < 0.002). In contrast, Ef-Arts became significantly constricted at concentrations as low as 10(-11) M with either perfusion. Surprisingly, the decrease in Ef-Art diameter at 10(-10), 10(-9), and 10(-8) M was significantly greater with retrograde perfusion (44 +/- 6.9%, 70 +/- 5.6%, and 74 +/- 4.1%, respectively; n = 5) than with orthograde perfusion (16 +/- 4.2%, 25 +/- 2.9%, and 35 +/- 3.5%; n = 9). ENDO synthesis inhibition with 10(-4) M nitro-L-arginine methyl ester (L-NAME) decreased the diameter to a greater extent in Af-Arts (22 +/- 3.0%; n = 11) compared to Ef-Arts with either orthograde (9.5 +/- 2.3%; n = 8) or retrograde perfusion (1.2 +/- 2.1%; n = 6). With L-NAME pretreatment, Af-Art constriction induced by 10(-10) M (14 +/- 4.0%, n = 9) and 10(-9) M Ang II (38 +/- 3.9%) was significantly greater compared to nontreated Af-Arts. In contrast, L-NAME pretreatment had no effect on Ang II-induced constriction in Ef-Arts with either perfusion. In conclusion, this study demonstrates higher sensitivity of Ef-Arts to Ang II, particularly with retrograde perfusion. Our results suggest that EDNO significantly modulates the vasoconstrictor action of Ang II in Af-Arts II but not Ef-Arts, contributing to the differential sensitivity to Ang II.

Possible role of P-450 metabolite of arachidonic acid in vasodilator mechanism of angiotensin II type 2 receptor in the isolated microperfused rabbit afferent arteriole.

Although angiotensin II type 2 (AT2) receptor has recently been cloned, its functional role is not well understood. We tested the hypothesis that selective activation of AT2 receptor causes vasodilation in the preglomerular afferent arteriole (Af-Art), a vascular segment that accounts for most of the preglomerular resistance. We microperfused rabbit Af-Arts at 60 mmHg in vitro, and examined the effect of angiotensin II (Ang II; 10(-11)-10(-8) M) on the luminal diameter in the presence or absence of the Ang II type 1 receptor antagonist CV11974 (CV; 10(-8) M). Ang II was added to both the bath and lumen of preconstricted Af-Arts. Ang II further constricted Af-Arts without CV (by 74+/-7% over the preconstricted level at 10(-8) M; P < 0.01, n = 7). In contrast, in the presence of CV, Ang II caused dose-dependent dilation; Ang II at 10(-8) M increased the diameter by 29+/-2% (n = 7, P < 0.01). This dilation was completely abolished by pretreatment with an AT2 receptor antagonist PD123319 (10(-7) M, n = 6), suggesting that activation of AT2 receptor causes vasodilation in Af-Arts. The dilation was unaffected by inhibiting either nitric oxide synthase (n = 7) or cyclooxygenase (n = 7), however, it was abolished by either disrupting the endothelium (n = 10) or inhibiting the cytochrome P-450 pathway, particularly the synthesis of epoxyeicosatrienoic acids (EETs, n = 7). These results suggest that in the Af-Art activation of the AT2 receptor may cause endothelium-dependent vasodilation via a cytochrome P-450 pathway, possibly by EETs.

A sedimentation equilibrium study of the temperature-dependent association of bovine beta-casein.

The temperature-dependent association of beta-casein was studied by the sedimentation equilibrium method. The weight-average molecular weight of the protein was determined in 0.2 M sodium phosphate buffer (pH 6.7) at 20, 15, 10 and 2 degrees C, and was found to be dependent markedly on both temperature and protein concentration. The data were well fitted by a monomer-n-mer association scheme, and the values of n, the second viral coefficient, and the free energy change for the association (association constant) were evaluated. The results show that temperature not only shifts the equilibrium but alters the polymer size: the values of n are 49, 22, and 12 at 20, 15, and 10 degrees C, respectively; the free energy change per monomer becomes more negative with increasing temperature, indicating that the attraction between the monomers in a polymer is stronger at higher temperature. This effect of temperature is in contrast to that of ionic strength which affects mainly the equilibrium. The enthalpy change, entropy change, and heat capacity change for the association were also estimated and were indicative of the formation of a considerable amount of hydrophobic bonds upon association.

Early assessment of reperfusion therapy using cardiac troponin T.

OBJECTIVES: The purpose of this study was to investigate the utility of cardiac troponin T for early assessment of reperfusion therapy. BACKGROUND: Several biochemical markers are used for early noninvasive detection of reperfusion during intravenous thrombolytic therapy. However, cardiac troponin T, a new myocardial-specific marker, has not been used previously for this purpose. METHODS: We measured troponin T and creatine kinase, MB isoenzyme (CK-MB) levels in 38 patients with acute myocardial infarction whose infarct-related artery was totally occluded before reperfusion therapy. Subjects comprised 14 patients with successful angioplasty (group 1), 12 patients with successful thrombolytic therapy (group 2) and 12 patients with unsuccessful attempted reperfusion (group 3). Blood samples were taken every 15 min, and coronary angiography was performed every 5 to 8 min until 60 min after reperfusion (groups 1 and 2) or after the initiation of treatment (group 3). We calculated the increase in troponin T (delta troponin T) and CK-MB (delta CK-MB) 60 min after treatment was initiated and 60 min after reperfusion in groups 1 and 2. RESULTS: Mean (+/- SD) delta troponin T and delta CK-MB levels were 9.35 +/- 7.83 ng/ml and 125 +/- 83 mU/ml in group 1 and 3.23 +/- 3.08 ng/ml and 130 +/- 137 mU/ml in group 2, respectively, 60 min after treatment and were 10.1 +/- 8.35 ng/ml and 131 +/- 84 mU/ml in group 1 and 6.84 +/- 8.30 ng/ml and 158 +/- 146 mU/ml in group 2, respectively, 60 min after reperfusion. These values were significantly higher than those 60 min after treatment in group 3: 0.16 +/- 0.19 ng/ml and 10 +/- 9 mU/ml, respectively. The predictive accuracy for detecting reperfusion using a threshold value of 0.50 ng/ml of delta troponin T and 25 mU/ml of delta CK-MB was 100% in group 1 and 92% in group 2 60 min after treatment, respectively. There was significant correlation between delta troponin T and delta CK-MB. CONCLUSIONS: Serial measurements of cardiac troponin T as well as of CK-MB are useful for early assessment of reperfusion therapy.

Rapid diagnosis of coronary reperfusion by measurement of myoglobin level every 15 min in acute myocardial infarction.

OBJECTIVES: The purpose of this study was to examine whether coronary reperfusion can be diagnosed rapidly and accurately by myoglobin measurements. BACKGROUND: When intravenous thrombolysis is used for acute myocardial infarction, it is important to determine coronary reperfusion rapidly and noninvasively so that further treatment can be initiated. METHODS: We determined myoglobin, creatine kinase (CK) and creatine kinase, MB fraction (CK-MB) isoenzyme levels in 63 patients with acute myocardial infarction with total occlusion of the infarct-related artery that was confirmed by coronary angiography. Myoglobin was measured by turbidimetric latex agglutination, which has an assay time of 10 min. We measured myoglobin, CK and CK-MB every 15 min in 45 patients with and 18 patients without reperfusion. The condition of the infarct-related artery was confirmed every 5 to 8 min by coronary angiography. RESULTS: The rate of increase in myoglobin, CK, and CK-MB at 15, 30, 45 and 60 min after treatment and reperfusion was significantly higher in the reperfused than in the nonreperfused group. In the reperfused group, the rate of increase in myoglobin was significantly higher than the corresponding rate of increase in CK and CK-MB at 15, 30 and 45 min after reperfusion. When reperfusion was evaluated on the basis of a cutoff level (myoglobin > or = 2.0, CK > or = 1.8, CK-MB > or = 1.5), the predictive accuracy of myoglobin (95%) was significantly higher than that of CK (68%) and CK-MB (73%) at 15 min after reperfusion. CONCLUSIONS: Coronary reperfusion can be rapidly and accurately detected by measurement of the plasma myoglobin every 15 min.

Effect of low-intensity training on transient kinetics of pulmonary oxygen uptake during moderate-intensity cycle exercise.

AIM: It is unclear whether the slowed time constant of phase II in pulmonary oxygen uptake on-kinetics (V̇O2τ) in unfit and inactive men would be shortened by low exercise intensity (low-intensity) walking training. We therefore tested the hypothesis that the slowed V̇O2τ in sedentary population would speed up due to low-intensity walking training with high volume. METHODS: Ten unfit and inactive male subjects (aged 26 to 50 yrs) underwent a low-intensity (30-40% of V̇O2max), long-duration (>60 min) training in the form of walking exercise 3-4 times a week for 12 weeks. We prospectively collected data on anthropometric, maximal oxygen uptake (V̇O2max), time constant of heart rate (HRτ) and V̇O2τ before training (0 wk; Pre) and every six weeks (6 wk; Mid, 12 wk; Post) from the beginning of the training. RESULTS: Anthropometric variables and V̇O2max showed no significant changes throughout the training program, whereas HRτ showed a tendency to be shortened with a progress of the training with no significant change. The slowed V̇O2τ at Pre (47.6±5.6 s) remained almost unchanged at Mid (48.8±4.9 s), but had a significant decrease at Post (40.5±7.9 s, P<0.05). CONCLUSION: In this study acceleration of the slowed V̇O2τ due to low-intensity walking training is thought to occur presumably owing to an improved matching of oxygen delivery to oxygen utilization at the site of gas exchange in active muscle tissue. We concluded that low-intensity walking training at beginning stage of training could contribute to the acceleration of the slowed V̇O2τ in unfit and inactive subjects.

Transcriptional suppression of type 1 angiotensin II receptor gene expression by peroxisome proliferator-activated receptor-gamma in vascular smooth muscle cells.

Angiotensin (A) II plays a critical role in vascular remodeling, and its action is mediated by type 1 AII receptor (AT1R). Recently, 15-deoxy-(Delta)(12,14)-prostaglandin J(2) and thiazolidinediones have been shown to be ligands for peroxisome proliferator-activated receptor (PPAR)-gamma and activate PPAR-gamma. In the present work, we have studied the effect of PPAR-gamma on AT1R expression in rat vascular smooth muscle cells (VSMCs). We observed that: 1) endogenous AT1R expression was significantly decreased by PPAR-gamma ligands both at messenger RNA and protein levels, whereas AT1R messenger RNA stability was not affected; 2) AII-induced increase of (3)H-thymidine incorporation into VSMCs was inhibited by PPAR-gamma ligands; 3) rat AT1R gene promoter activity was significantly suppressed by PPAR-gamma ligands, and PPAR-gamma overexpression further suppressed the promoter activity; 4) transcriptional analyses using AT1R gene promoter mutants revealed that a GC-box-related sequence within the -58/-34 region of the AT1R gene promoter was responsible for the suppression; 5) Sp1 overexpression stimulated AT1R gene transcription via the GC-box-related sequence, which was inhibited by additional PPAR-gamma overexpression; 6) electrophoretic mobility shift assay suggested that Sp1 could bind to the GC-box-related sequence whereas PPAR-gamma could not; 7) antibody supershift experiments using VSMC nuclear extracts revealed that protein-DNA complexes formed on the GC-box-related sequence, which were decreased by PPAR-gamma coincubation, were mostly composed of Sp1; and 8) glutathione S-transferase pull-down assay revealed a direct interaction between PPAR-gamma and Sp1. Taken together, it is suggested that activated PPAR-gamma suppresses AT1R gene at a transcriptional level by inhibiting Sp1 via a protein-protein interaction. PPAR-gamma ligands, thus, may inhibit AII-induced cell growth and hypertrophy in VSMCs by AT1R expression suppression and possibly be beneficial for treatment of diabetic patients with hypertension and atherosclerosis.

20-HETE requires increased vascular tone to constrict rabbit afferent arterioles.

Renal production of 20-hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P-450-dependent arachidonate metabolite, increases during development of hypertension in spontaneously hypertensive rats, and inhibition of its production prevents hypertension. Since 20-HETE is a potent vasoconstrictor, these findings suggest that 20-HETE may contribute to the development of hypertension by elevating renal vascular resistance. In this study we examined the direct action of 20-HETE on the afferent arteriole, a vascular segment crucial to the control of renal vascular resistance. Rabbit afferent arterioles were microperfused at 60 mm Hg in vitro, and 20-HETE was added to the lumen. Although 20-HETE (10(-10) to 10(-6) mol/L) had no effect on the diameter of non-treated afferent arterioles (n=6), it caused dose-dependent constriction when vascular tone was increased with norepinephrine (0.3 micromol/L); 20-HETE at 10(-6) mol/L decreased diameter by 43 +/- 4% (n=6, P < .001). This constriction was abolished by disrupting the endothelium (n=5). Moreover, pretreatment with the cyclooxygenase inhibitor indomethacin (50 micromol/L) or the thromboxane/endoperoxide receptor antagonist SQ29548 (1 micromol/L) significantly (P < .03) attenuated 20-HETE-induced constriction: 20-HETE at 10(-6) mol/L constricted norepinephrine-treated afferent arterioles by 28 +/- 3% (n=6) and 25 +/- 4% (n=5), respectively. These results demonstrate that an increase in afferent arteriolar tone is required for the vasoconstrictor action of 20-HETE, which is partly mediated by the endothelial cyclooxygenase pathway. THus, increased production of 20-HETE in the kidney and increase in afferent arteriolar tone, both of which often precede the development of hypertension, may synergistically contribute to the development of hypertension by elevating renal vascular resistance.

A new predictor of restenosis after successful percutaneous transluminal coronary angioplasty in patients with multivessel coronary artery disease.

With the goal of improving prediction of restenosis after percutaneous transluminal coronary angioplasty (PTCA) for multivessel coronary artery disease (CAD), we evaluated the usefulness of serial exercise treadmill tests. We previously reported that an increase in the deltaST/delta heart rate (HR) index at follow-up over the value obtained several days after PTCA was useful for detecting restenosis following PTCA for 1-vessel CAD. In that report, comparison of the deltaST/deltaHR index was made based on measurements from the lead disclosing the greatest ST displacement before PTCA. This method was not applicable to patients with multivessel CAD. Seventy-eight patients with multivessel CAD before and several days after PTCA and just before follow-up performed exercise treadmill tests. Simple HR-adjusted indexes of ST-segment depression during exercise (deltaST/deltaHR index) and the sum of the deltaST/deltaHR index in leads II, III, aVF, V4, V5, and V6 (sigma deltaST/deltaHR index) were determined. We compared the predictive power of an increase in sigma deltaST/deltaHR index at follow-up with that of a positive exercise treadmill test and a positive thallium scintigram for restenosis. At follow-up, 37 of the 78 patients showed restenosis. The sigma deltaST/deltaHR index had increased in 30 of these 37 patients (81%), and in 12 of the 41 patients (29%) without restenosis. An increase in sigma deltaST/deltaHR index had a significantly higher sensitivity than the other methods and a significantly higher specificity than a positive exercise treadmill test.

Usefulness of adenosine triphosphate-atropine stress echocardiography for detecting coronary artery stenosis.

There have been few studies on adenosine triphosphate (AT) stress echocardiography. The AT stress test may have fewer adverse effects than the adenosine stress test. The addition of atropine to AT echocardiography may enhance the sensitivity for detection of coronary artery disease (CAD). The purpose of this study was to determine the utility of AT-atropine echocardiography for detection of CAD. The group studied consisted of 112 patients with suspected CAD. Sixty-one patients did not have a history of prior myocardial infarction (group I) and 51 patients did (group II). AT was infused intravenously at 180 microg/kg/min for 14 minutes. Atropine (0.25 mg intravenously, repeated up to maximum total dose of 1 mg) was administered starting after 8 minutes of AT infusion. Ischemic response was defined as new or worsening wall motion abnormality occurring during the infusion. The sensitivity and specificity for detection of CAD were assessed using the representative echocardiograms during single AT infusion and AT-atropine infusion. Sixty-two patients had CAD. Fifty-eight patients (52%) developed minor side effects that resolved promptly. The rate-pressure product (10(3)/mm Hg beats/min) was significantly increased at 12 minutes of infusion (12.4+/-3.2) compared with that at baseline (9.1+/-2.3) and that at 6 minutes of infusion (9.4+/-2.1). The sensitivity for detection of CAD was 45% for AT echocardiography and 74% for AT-atropine echocardiography. The specificity was 94% for AT echocardiography and 90% for AT-atropine echocardiography. The sensitivity and specificity of AT-atropine echocardiography was 78% and 93%, respectively, in group I, and 70% and 86%, respectively, in group II. In conclusion, AT-atropine stress echocardiography seems to be well tolerated, safe, and useful for detection of CAD.

Increase in the delta ST/delta heart rate (HR) index: a new predictor of restenosis after successful percutaneous transluminal coronary angioplasty.

With the goal of improving the prediction of restenosis after percutaneous transluminal coronary angioplasty (PTCA), we evaluated the usefulness of the delta ST/delta heart rate (HR) index derived from serial exercise treadmill tests. Exercise treadmill tests were performed by 125 patients with single-vessel coronary artery disease before and several days after PTCA, and just before follow-up angiography 3 to 12 months later. Simple HR-adjusted indexes of ST-segment depression during exercise (delta ST/delta HR index) were derived. We compared the usefulness of the increase in delta ST/delta HR index at follow-up over the value obtained several days after PTCA for prediction of restenosis with that of a positive exercise treadmill test and a positive thallium scintigram at follow-up. At follow-up, 47 of the 125 patients showed restenosis. The delta ST/delta HR index increased in 43 of 47 patients in the restenosis group and in 18 of 78 patients without restenosis (p < 0.0001). Separate analysis of each criterion revealed the following respective values for sensitivity, specificity, and positive and negative predictive values for prediction of restenosis; increased delta ST/delta HR index of follow-up: 91%, 77%, 70%, and 94%; positive exercise treadmill test: 83%, 65%, 59%, and 86%; and positive thallium scintigram: 79%, 78%, 69%, and 86%. The increased delta ST/delta HR index had a significantly (p < 0.05) higher sensitivity than the positive thallium scintigram and a significantly (p < 0.01) higher specificity than the positive exercise treadmill test. An increased delta ST/delta HR index at follow-up identifies subgroups of patients who are at high risk for restenosis after PTCA.

Mechanisms of limited maximum coronary flow in severe single-vessel coronary artery disease in humans due to vertical steal.

We evaluated the usefulness of a decrease in the average peak velocity from 4 to 10 minutes after infusion of dipyridamole for detecting myocardial ischemia in 50 patients, including patients with a prior myocardial infarction. The decrease in the average peak velocity from 4 to 10 minutes associated with vertical steal and combined with a coronary flow reserve of < 1.6 had a high predictive value for myocardial ischemia in patients with or without prior myocardial infarction.

Right ventricular stiffness measured by a new method without volume estimation in coronary artery disease.

This study was designed to measure the right ventricular (RV) stiffness (delta P/ delta V) with a new method without estimating the RV volume itself. RV stiffness has rarely been measured due to the difficulty in estimating the RV volume. Without measuring RV volume itself, stiffness can be determined by measuring its volume change (delta V). Tricuspid filling flow volume, which is the diastolic RV delta V, is measurable by using Doppler echocardiography. Thus, RV stiffness may possibly be obtained from Doppler echocardiography combined with high-fidelity RV pressure. Subjects consisted of 8 controls, 8 patients with angina pectoris, 8 with anterior, 8 with posterior, and 8 with inferior prior myocardial infarction. Tricuspid annular dimension was measured by 2-dimensional echocardiography and the tricuspid annular area was calculated. Velocity-time integral of the tricuspid filling flow during the late diastole was measured by pulsed Doppler echocardiography. Then, the late diastolic RV delta V was obtained as the product of the tricuspid annular area and the integral. The late diastolic RV pressure rise (delta P) was also measured with a micromanometer catheter. The RV elastic chamber stiffness constant ([delta P/ delta V]/P) was obtained by dividing simple stiffness by the mean RV pressure during late diastole. The RV elastic chamber stiffness constant did not significantly differ among controls, patients with angina pectoris, and those with anterior and posterior myocardial infarction (0.0054 +/- 0.0009 vs 0.0057 +/- 0.0018 vs 0.0064 +/- 0.002 vs 0.0052 +/- 0.0019 ml-1). However, it was significantly increased in patients with inferior myocardial infarction (0.010 +/- 0.004 ml-1, p < 0.01 or 0.05) compared with those in the other 4 groups. These results suggest (1) that RV stiffness can be measured with a new method without RV volume estimation, and (2) that this new method is useful in evaluating RV diastolic pathophysiology in patients with coronary artery disease.

A new criterion combining ST/HR slope and deltaST/deltaHR index for detection of coronary artery disease in patients on digoxin therapy.

We evaluated the clinical value of a new index combining deltaST/delta heart rate (HR) index and ST/HR slope for diagnosing coronary artery disease (CAD) in patients on digoxin therapy. Exercise treadmill tests were performed by 72 patients on digoxin therapy. Simple HR-adjusted indexes of ST-segment depression during exercise (deltaST/deltaHR index) and the decline calculated from the final 12 data points relating ST-segment depression to HR (ST/HR slope) were determined. A new index was obtained by subtracting the deltaST/deltaHR index from the ST/HR slope. On thallium scintigraphy, 37 of the 72 patients showed reversible perfusion defects related to the diseased coronary artery. The new index derived from this ST-HR relation was 4.1 +/- 3.6 microV/beats/min in the ischemic group and 1.3 +/- 1.0 microV/beats/min in the group of patients without ischemia (p <0.0001). An ST-HR relation > or = 1.5 was found in 33 of the 37 patients in the ischemic group, and in 7 of the 35 patients without ischemia (p <0.0001). The sensitivity of this criterion for prediction of myocardial ischemia was 89%, the specificity was 80%, and the predictive accuracy was 85%. Thus, this new ST-HR index is useful for detecting CAD in patients on digoxin therapy.

New insights into actions of the renin-angiotensin system in the kidney: concentrating on the Ang II receptors and the newly described Ang-(1-7) and its receptor.

Angiotensin II (Ang II), the physiologically active component of the renin-angiotensin system (RAS), plays an important role in the regulation of the renal function. Based on their different pharmacologic and biochemical properties, 2 distinct subtypes of Ang II receptor have been defined and designated as type 1 (AT(1)) and type 2 (AT(2)) receptors. Most of the well-characterized actions of Ang II are now generally considered to result from stimulation of AT(1) receptors, whereas AT(2) receptors may exert opposite effects against AT(1) receptors. In the kidney, activation of the AT(2) receptor has been reported to regulate pressure-natriuresis and to stimulate the production of nitric oxide, bradykinin, or epoxyeicosatrienoic acids, which may cause vasodilation and modulate the vasoconstrictor action mediated by AT(1) receptors. In addition, recent studies have reported that Ang II exerts important effects on the normal renal development through both AT(1) and AT(2) receptors. Finally, other Ang fragments such as Ang-(1-7) are also involved in the actions of RAS in the kidney. In this review article, we will summarize results obtained from recent studies on the AT(1) and AT(2) receptor-mediated action of Ang II in the kidney. Renal actions of Ang-(1-7), which often oppose against those of Ang II, are also discussed.

Heterogeneity of angiotensin action in renal circulation.

Reported concentrations of angiotensin II (Ang II) in renal interstitial fluid are as high as 10 nM. Despite such high concentrations, intrarenal arterial infusion of Ang II at rates that induce far less change in renal Ang II concentration still elicits renal vasoconstriction. We examined whether the glomerular afferent arterioles (Af-Art) was more sensitive to intraluminal than extraluminal Ang II in superficial or juxtamedullary nephrons. Rat superficial Af-Arts with the intact glomerulus were microdissected and perfused in vitro at 70 mmHg, while juxtamedullary Af-Arts were visualized in isolated perfused kidneys (at 100 mm Hg) according to the method of Casellas and Navar. Increasing doses of Ang II (1 pM to 10 nM) or norepinephrine (NE; 1 nM to 1 microM) were added to either bath (extraluminal) or arteriolar perfusate (intraluminal). Decreases in luminal diameter induced by Ang II were significantly larger with intraluminal than extraluminal administration in superficial Af-Art: at 100 pM the diameter decreased by 52 +/- 8% (N = 6) and 7 +/- 3% with intraluminal and extraluminal administration, respectively. In contrast, in the juxtamedullary Af-Arts intraluminal and extraluminal Ang II caused similar constriction. On the other hand, there was no difference in intraluminal versus extraluminal NE action in either superficial or juxtamedullary nephrons. In conclusion, glomerular Af-Arts seem to have a higher sensitivity to luminal than interstitial Ang II in superficial but not juxtamedullary nephrons. Such heterogeneities in Ang II action may be important in the control of glomerular hemodynamics under various physiological and pathological conditions.

Function of angiotensin II type 2 receptor in the postglomerular efferent arteriole.

The balance of vasucular tone between afferent (Af-Art) and efferent arterioles (Ef-Art) is a critical determinant of the glomerular hemodynamics. We recently reported that selective activation of angiotensin II type 2 receptor (AT-2R) causes dilation in the Af-Art. However, the functional role of AT-2R in the Ef-Art has not been defined. In the present study, we microperfused rabbit Ef-Art in vitro, and examined the effect of angiotensin II (Ang II; 10(-11) to 10(-8) M) on the luminal diameter in the presence or absence of an AT-2R antagonist PD123319 (PD; 10(-7) M). Angiotensin II caused dose-dependent constriction in Ef-Arts, with a significant constriction occurring at 10(-11) M; at 10(-10) M the diameter decreased by 28 +/- 4% (N = 6). Pretreatment with PD significantly (P < 0.0125) augmented vasoconstrictor action of Ang II; at 10(-10) M the diameter decreased by 44 +/- 4% (N = 6). We then examined whether blockade of Ang II type 1 receptor (AT-1R) uncovers vasodilator action of Ang II mediated by AT-2R. Efferent arterioles were preconstricted by about 40% with norepinephrine and AT-1R was blocked with its selective antagonist CV11974 (CV; 10(-8) M). Angiotensin II added to preconstricted and CV-pretreated Ef-Arts caused a dose-dependent dilation; at 10(-8) M diameter increased by 28 +/- 3% (N = 5). The dilation was completely abolished by simultaneous pretreatment with PD (N = 4). Our results demonstrate that in the Ef-Art selective activation of AT-2R causes vasodilation, which opposes the vasoconstrictor action of Ang II.