Two-dimensional echocardiographic scoring system of the left ventricular filling pressure and clinical outcomes in heart failure with preserved ejection fraction

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): Japan Society for the Promotion of Science (JSPS)

Introduction

Elevated left ventricular (LV) filling pressure in non-decompensated state is a powerful indicator of worse clinical outcomes in heart failure regardless of LV ejection fraction. However, its detection is often challenging in heart failure with preserved ejection fraction (HFpEF).

Purpose

This study aimed to elucidate the predictive value of recently proposed echocardiographic parameter of LV filling pressure, Visually assessed time difference between the Mitral valve and Tricuspid valve opening (VMT) score in HFpEF.

Methods

We retrospectively analyzed 310 well-differentiated HFpEF patients in stable conditions. Using two-dimensional echocardiographic images, time sequence of opening of mitral valve and tricuspid valve was visually assessed in the apical four-chamber view and scored to 0 to 2 (0: tricuspid valve first, 1: simultaneous, 2: mitral valve first). When the inferior vena cava diameter was dilated, 1 point was added and VMT score was calculated as four grades from 0 to 3. Based on the previous study, VMT≥2 was regarded as a sign of elevated LV filling pressure (Figure 1). LV diastolic function was graded according to the guidelines. The primary endpoint was defined as a composite of cardiac death and heart failure hospitalisation during the two years after echocardiographic examination.

Results

During the follow-up period, 55 events (18%) occurred, including four cardiac deaths and 51 heart failure hospitalisations. Kaplan-Meier curves demonstrated that VMT≥2 (n = 54) was associated with worse outcomes compared to patients showing VMT ≤ 1 (n = 256) (log-rank test P <0.001). Furthermore, VMT≥2 was associated with worse outcomes when tested in 100 HFpEF patients with atrial fibrillation (log-rank test P = 0.026) (Figure 2). In the adjusted model including age, systolic blood pressure, serum albumin level, and the LV diastolic function grading, VMT≥2 was independently associated with the primary outcome (hazard ratio: 2.23; 95% confidence interval: 1.17 to 4.24, P = 0.014). Additionally, the nested regression model showed that VMT scoring provided an incremental prognostic value over clinically relevant variables (age, sex, the plasma brain natriuretic peptide level, atrial fibrillation) and LV diastolic function grading (chi-square 10.8 vs 16.3, P = 0.035).

Conclusions

In patients with HFpEF, the VMT score was independently and incrementally associated with adverse clinical outcomes. Moreover, it discriminated worse clinical outcome even in HFpEF patients with atrial fibrillation. Abstract Figure. VMT scoring  Abstract Figure. Kaplan-Meier analysis

Pathophysiological mechanism of worsened clinical outcome by lowered left ventricular cardiac power output in heart failure

Funding Acknowledgements

Type of funding sources: None.

Background

Cardiac power output (CPO) is a measure of cardiac pumping function, and CPO during exercise is known to be a powerful prognostic marker of heart failure. Despite its prognostic significance, pathophysiological mechanism of the association between reduced CPO and worse clinical outcome is unknown. We hypothesized that reduced CPO is associated with worse outcome through the reduced exercise capacity and enhanced ventilatory response.

Methods

Cardiopulmonary exercise testing and exercise stress echocardiography were performed in consecutive 64 patients with chronic heart failure who admitted to our department for the management of heart failure [60 ± 14 years old, left ventricular (LV) ejection fraction 39 ± 16%, ischemic etiology 16%, brain natriuretic peptide 124 pg/ml (51-313)]. Peak oxygen uptake (peak VO2) and the lowest minute ventilation / carbon dioxide production ratio (VE/VCO2) were measured as a parameter of exercise tolerance and that of ventilatory response, respectively. LV ejection fraction was measured by disk summation method at peak exercise. By using Doppler images, E/e" at peak exercise was measured as a marker of LV filling pressure, and CPO normalized by LV mass was obtained as 0.222 × cardiac output × mean blood pressure / LV mass [W/100 g]. Cardiac events defined as hospitalization for heart failure, cardiac death, or implantation of a LV assist device after the examinations were recorded.

Results

CPO at rest was weakly correlated with peak VO2 (r = 0.25, p = 0.046) but not with VE/VCO2. In contrast, CPO at peak exercise was positively correlated with peak VO2 (r = 0.50, p < 0.001) and inversely correlated with VE/VCO2 (r=-0.40, p = 0.002). Moreover, CPO at peak exercise determined both peak VO2 (b = 0.50) and VE/VCO2 (β=-0.54) independently of LV ejection fraction and E/e" at peak exercise. During a median follow-up period of 1211 days, 12 cardiac events were observed. Each of reduced peak VO2 (hazard ratio 0.78, 95% confidence interval 0.66-0.90) and increased VE/VCO2 (hazard ratio 1.10, 95% confidence interval 1.02-1.18) was associated with worse clinical outcome.

Conclusions

In patients with chronic heart failure, CPO during exercise was associated with prognosis of heart failure through the reduced exercise capacity and enhanced ventilatory response.

Applicability of the AHA/ACC/HRS guideline for implantable cardioverter defibrillator implantation in Japanese patients with cardiac sarcoidosis

Background

Sarcoidosis is a systemic granulomatous disease that affects multiple organs. Cardiac involvement is a key determinant of poor clinical outcomes in the patients with sarcoidosis, as it causes congestive heart failure, conduction abnormalities, ventricular tachycardia and fibrillation (VT/VF), and sudden cardiac death (SCD). Although implantable cardioverter defibrillators (ICDs) are used to prevent SCD from VT/VF in patients with cardiac sarcoidosis (CS), the generalizability of the AHA/ACC/HRS guidelines for the Japanese CS patients remains unclear.

Purpose

We aimed to assess, among Japanese patients with CS, the ICD recommendations from the 2017 AHA/ACC/HRS Guidelines for Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death.

Methods

We examined 188 consecutive patients with CS in two tertiary hospitals between 1979 and 2020. The primary outcome was defined as a composite outcome involving SCD or ventricular arrhythmic events. Ventricular arrhythmic events were defined as either emergency treatment for VF or sustained VT, which included appropriate ICD therapy.

Results

During a median follow-up period of 5.68 (IQR: 4.87–6.70) years, the primary outcome occurred in 44 patients (23%), which included 6 cases of SCD and 38 cases of VT/VF. ICD implant was indicated based on left ventricular ejection fraction (LVEF) of ≤35% (class I recommendation) in 62 patients, with an annualized event rate of 3.93%. A LVEF of >35% with a need for a permanent pacemaker (class IIa recommendation) was observed for 53 patients, with an annualized event rate of 2.54%. A LVEF of >35% with late gadolinium enhancement (LGE) during cardiovascular magnetic resonance (class IIa recommendation) was observed for 62 patients, with an annualized event rate of 2.38% (Figure A). Kaplan-Meier analyses revealed that patients with a class I recommendation for ICD implantation had a significant higher incidence of the primary outcome, compared to patients with a class IIa recommendation and patients with no indication for ICD implantation (P=0.03). However, there were no significant differences in the incidence of the primary outcome between patients with a LVEF of >35% and a need for a permanent pacemaker and patients with a class I recommendation (P=0.08) or patients with a LVEF of ≤35% (P=0.31). Moreover, there was no significant difference in the incidence of the primary outcome between patients with a LVEF of >35% and LGE on cardiovascular magnetic resonance and patients with a class I recommendation (P=0.054) or patients with a LVEF of ≤35% (P=0.22) (Figure B).

Conclusions

The American guideline recommendations for ICD implantation might be applicable to Japanese patients with CS. Implantation of an ICD may need to be considered in these patients if they require a permanent pacemaker or have LGE, regardless of LVEF.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Japan Society for the Promotion of Science

Influence of left ventricular systolic dysfunction on occurrence of pulsus tardus in patients with aortic stenosis

Funding Acknowledgements

Type of funding sources: None.

Background

The time between left ventricular (LV) and aortic systolic pressure peaks (TLV-Ao) which could reflect pulsus tardus (PT) is reported to be a marker of severity and be associated with poor prognosis in patients with aortic stenosis (AS). Despite its worldwide recognition, physiological mechanism of PT has not been well elucidated. We hypothesized that not only severity of the AS but also LV systolic dysfunction could be associated with occurrence of PT.

Methods

TLV-Ao and mean trans-aortic valvular pressure gradient (mean PG) were measured by simultaneous pressure tracing of left ventricle and basal aorta in 74 AS patients with at least moderate severity (78 ± 8 years old). Effective orifice area index (EOAI) was estimated by using continuity equation from transthoracic echocardiography and severe AS was defined as EOAI ± 0.60 cm²/m². Global longitudinal strain (GLS) was measured by using speckle-tracking method and expressed as an absolute value.

Results

TLV-Ao, mean PG, and EOAI was 87 ± 30 msec, 51 ± 21 mmHg, and 0.51 ± 0.14 cm² respectively. A weak correlation was observed between EOAI and TLV-Ao (Figure). In 9 out of 17 moderate AS patients (A in Figure), TLV-Ao was prolonged over the previously reported cut-off value (≥66 msec), on the other hand, it was not prolonged in 11 out of 57 severe AS patients (D in Figure). When the patients were divided by TLV-Ao of 66 msec, mean PG was not different between patients with prolonged TLV-Ao and those without in moderate AS patients (Figure, A vs B; NS), whereas GLS was significantly reduced in prolonged TLV-Ao group (P = 0.0383). In patients with severe AS, mean PG was significantly higher (P < 0.0001) in patients with prolonged TLV-Ao than in those without (Figure, C vs D), whereas GLS was comparable between the groups. In overall patients, multivariable analysis revealed that not only mean PG (β=0.54) but also GLS (β=-0.23) was an independent determinant of TLV-Ao.

Conclusion

The occurrence of pulsus tardus could be associated not only with severity of the AS but also with LV systolic dysfunction in patients with AS.

Abstract Figure

Presence and significance of mid-systolic notch on right ventricular outflow tract velocity envelopes in pulmonary hypertension due to heart failure

Funding Acknowledgements

Type of funding sources: None.

Background

 A mid-systolic notch (MSN) of the right ventricular outflow tract (RVOT) pulsed-wave Doppler envelope, which is recognized as a characteristic finding in pre-capillary pulmonary hypertension (PH), is often observed in heart failure (HF) patients. However, clinical significance of MSN formation in HF has not been elucidated.

Methods

 Consecutive 233 HF patients who underwent right heart catheterization and echocardiography within 24 hours were enrolled. Isolated post-capillary PH (IpcPH) was defined as mean pulmonary arterial pressure (mPAP) >20 mmHg, mean pulmonary artery wedge pressure (mPAWP) >15 mmHg, and pulmonary vascular resistance (PVR) <3 Wood units and combined pre- and post-capillary PH (CpcPH) was as mPAP >20 mmHg, mPAWP >15 mmHg, and PVR ≥3 Wood units. Pulmonary arterial capacitance (PAC) was calculated as stroke volume / pulmonary arterial pulse pressure [mL/mmHg]. MSN was defined as formation of notch within first half of the RVOT pulsed-wave Doppler envelope.

Results

 Prevalence of IpcPH, CpcPH, and without PH were 87 (37%), 45 (19%), and 101 (43%), respectively and MSN was observed in 8 (9%) of IpcPH, 17 (38%) of CpcPH, and 1 (1%) of patients without PH. Among the hemodynamic and echocardiographic parameters, mPAP and PAC independently determined occurrence of MSN in all the multivariable models (Table). Interestingly, when the PH patients were dimidiated according to median PAC (3.2 mL/mmHg), 25 out of 102 PH patients (25%) with low PAC showed MSN whereas any of PH patients with high PAC did not (Figure).

Conclusion

 MSN was frequently observed in HF patients showing CpcPH. Combination of elevated pressure and reduced compliance of the pulmonary circulation could determine occurrence of MSN in HF.

Determinants of MSN occurrence Univariable analysis Multivariable analysis Model 1 Model 2 Model 3 Model 4 variables OR (95% CI) p OR (95% CI) p OR (95% CI) p OR (95% CI) p OR (95% CI) p LV ejection fraction 0.97 (0.94-0.99) 0.007 1.00 (0.96-1.03) 0.795 LV mass index 1.00 (1.00-1.02) 0.143 PAW pressure 1.13 (1.08-1.18) <0.001 0.92 (0.82-1.03) 0.135 Mean PA pressure 1.14 (1.09-1.19) <0.001 1.08 (1.02-1.14) 0.006 1.15 (1.04-1.27) 0.004 1.08 (1.00-1.17) 0.030 1.07 (1.01-1.14) 0.025 Mean RA pressure 1.14 (1.06-1.22) <0.001 1.00 (0.90-1.11) 0.978 Pulmonary vascular resistance 1.97 (1.45-2.67) <0.001 1.20 (0.88-1.63) 0.225 Pulmonary arterial capacitance 0.27 (0.15-0.48) <0.001 0.49 (0.26-0.92) 0.010 0.44 (0.23-0.85) 0.004 0.47 (0.24-0.93) 0.011 0.49 (0.26-0.93) 0.011 Abstract Figure.

Simple echocardiographic scoring system to estimate left ventricular filling pressure based on visual assessment of time sequence of mitral and tricuspid valve opening

Introduction

In the presence of elevated left ventricular (LV) filling pressure, mitral valve (MV) becomes to open early and precedes tricuspid valve (TV) opening in early diastole. Accordingly, time-delay of right ventricular inflow relative to LV inflow assessed by dual Doppler system was recently reported as a parameter of LV filling pressure. We assumed that visually-assessed time-delay of TV relative to MV opening could be a simple and alternative marker of elevated LV filling pressure.

Purpose

This study aimed to elucidate the clinical usefulness of the 2-dimensional echocardiographic scoring system, Visual assessment of time-difference between Mitral and Tricuspid valve opening (VMT) score, in patients with heart failure (HF).

Methods

We analyzed 119 consecutive HF patients who underwent echocardiography and cardiac catheterization within a day. Elevated LV filling pressure was defined as mean pulmonary arterial wedge pressure (PAWP) ≥15 mmHg. LV diastolic function was graded according to the ASE/EACVI recommendations. Time sequence of opening of MV and TV was visually assessed in the apical 4-chamber view and scored to 3 grades (0: TV opening first, 1: simultaneous, 2: MV opening first). When the inferior vena cava diameter was >21 mm and collapsed <20% during normal respiration, 1 point was added and VMT score was calculated as 4 grades from 0 to 3. We also investigated 113 patients without worsening HF at VMT scoring for cardiac events defined as worsening HF, LV assist device implantation, or cardiac death for 1 year after the echocardiography.

Results

VMT was scored as 0 in 20 patients, 1 in 50 patients, 2 in 37 patients, and 3 in 12 patients. PAWP was elevated in patients with VMT score of 2 and 3 (0: 10±5, 1: 12±4, 2: 22±8, 3: 28±4 mmHg, ANOVA P<0.001) (Figure). In overall patients, VMT≥2 predicted elevated PAWP with accuracy of 86%. When the accuracy was tested in patients with reduced (<40%, HFrEF) and preserved LV ejection fraction (≥40%) respectively, the accuracy was excellent in HFrEF (96% and 77%, respectively). Importantly, VMT≥2 also had good accuracy of 82% for elevated PAWP in 33 patients in whom recommendations usually cannot grade diastolic function due to monophasic LV inflow. In the sequential Cox models, the addition of VMT score to the model including the plasma brain natriuretic peptide (BNP) level and LV diastolic grading improved the predictive power for elevated PAWP (P<0.001). During the follow-up, 20 cardiac events were observed (6 worsening HF, 9 LV assist device implantation and 5 cardiac death). Kaplan-Meier analysis showed that the patients with VMT≥2 were at higher risk of cardiac events than those with VMT≤1 (log-rank test P<0.001) (Figure).

Conclusions

The VMT score was a simple and accurate marker of elevated LV filling pressure and has an incremental benefit over BNP and LV diastolic function grading. Moreover, it could be a novel prognostic marker in patients with HF.

Figure 1

Funding Acknowledgement

Type of funding source: None

Long-term prognostic significance of dispersion of ventricular repolarization in patients with cardiac sarcoidosis

Background

Although the presence of cardiac involvement is recognised as a determinant of worse clinical outcomes in sarcoidosis patients, the determinants of adverse outcomes in patients with cardiac sarcoidosis (CS) have not been well understood. T-peak to T-end interval (TpTe) on the surface electrocardiogram (ECG) was proposed as a marker of dispersion of ventricular repolarisation. Prolonged TpTe to QT interval ratio (TpTe/QT) represents a period of potential vulnerability to reentrant ventricular arrhythmias. Notably, prolonged TpTe/QT has been associated with increased risk of mortality in hypertrophic cardiomyopathy, congenital long-QT syndrome, and Brugada syndrome. However, its prognostic implication in patients with CS is unclear.

Purpose

We sought to investigate whether TpTe/QT was associated with long-term clinical outcomes in patients with CS.

Methods

A total of 108 consecutive CS patients between August 1986 and March 2019 in two academic hospitals who had ECG data before initiation of immunosuppressive therapy were examined. We excluded patients who received pacemaker (n=15) or cardiac resynchronization therapy (n=3) at the time of ECG. Ultimately, 90 CS patients were included in this study. All standard 12-lead ECGs were recorded at 25 mm/s with an amplification of 10 mm/mV. TpTe was measured from the peak of T wave to the end of T wave which defined as the intersection of the tangent to the down slope of the T wave and the isoelectric line. Lead V5 was selected for the analyses. If V5 is not suitable for analyses, V4 was selected. The primary outcome was the composite of advanced atrioventricular block (AVB), ventricular tachycardia or ventricular fibrillation (VT/VF), heart failure hospitalisation and all-cause death.

Results

During a median follow-up period of 4.70 (interquartile range [IQR] 2.06–7.23) years, adverse events occurred in 21 patients (23.3%), including 2 advanced AVB, 12 VT/VF, 4 heart failure hospitalisation and 3 all-cause death. Events group had higher TpTe/QT compared to no events group (0.231 [IQR 0.193–0.261] vs. 0.282 [IQR 0.263–0.304] P<0.001). Kaplan-Meier analyses revealed that the primary outcome, especially VT/VF or sudden cardiac death more frequently occurred in patients with higher TpTe/QT (≥0.242, the median) compared to those with lower TpTe/QT (Figure 1). Multivariable Cox regression analysis showed that higher TpTe/QT was independently associated with increased subsequent risk of adverse events (hazard ratio 1.09, 95% confidence interval [CI] 1.02–1.17, P=0.014) even after adjustment for age, sex and left ventricular ejection fraction. Furthermore, the optimal cut-off value of TpTe/QT for the discriminatory of primary outcome was 0.257, and c-index was 0.77 (95% CI 0.64–0.89).

Conclusions

Higher TpTe/QT was associated with worse long-term clinical outcomes in patients with CS. Our findings indicate the importance of assessing TpTe/QT for risk stratification in patients with CS.

Figure 1

Funding Acknowledgement

Type of funding source: None

P2634Prognostic value of admission left ventricular outflow tract velocity time integral in hospitalized heart failure patients with preserved ejection fraction: a report from the JASPER registry

Background

There are little effective treatment strategies for heart failure with preserved ejection fraction (HFpEF) to achieve a reduction of morbidity and mortality. Thus, accurate prognostication of patients with HFpEF could help improve their outcomes by identifying high-risk patients who might potentially benefit from intensive inpatient and outpatient monitoring and early referral for advanced HFpEF therapy. The left ventricular outflow tract velocity time integral (LVOT-VTI) is a representative non-invasive parameter for evaluating stroke volume, which can be a determinant of adverse outcomes in hospitalized patients with heart failure. However, the prognostic implication of admission LVOT-VTI for hospitalized HFpEF patients is undetermined.

Purpose

The aim of the present study was to investigate whether admission LVOT-VTI could predict poor clinical outcomes in hospitalized patients with HFpEF.

Methods

We examined consecutive 535 hospitalized HFpEF patients (left ventricular ejection fraction ≥50%) due to acute decompensated heart failure from the JASPER (JApanese heart failure Syndrome with Preserved Ejection fRaction) multicenter registry, obtained between November 2012 and March 2015. Patients without accessible LVOT-VTI data on admission were excluded. Finally, 214 patients were examined. The primary outcome of interest was composite of all-cause death and rehospitalization due to heart failure.

Results

Mean age was 78±11 years, 100 were male, and median plasma brain-type natriuretic peptide level was 400 (interquartile range [IQR] 223–711) pg/ml. During a median follow-up period of 688 (IQR 162–810) days, adverse events occurred in 83 patients (39%), including 47 (22%) all-cause death, 51 (24%) rehospitalization due to heart failure. The c-index of LVOT-VTI for predicting the composite of adverse events was 0.59 (95% CI 0.51 to 0.67), and the optimal cut-off value of LVOT-VTI was 15.8 cm. Low LVOT-VTI (≤15.8 cm) was significantly associated with higher adverse events compared to high LVOT-VTI (>15.8 cm) (Figure). Multivariable Cox regression analysis revealed that lower LVOT-VTI was an independent determinant of adverse events (HR 0.94, 95% CI 0.91 to 0.98, P=0.005) even after adjustment for pre-specified confounders including age, sex, systolic blood pressure, serum sodium, albumin, plasma brain-type natriuretic peptide and renal function.

Figure 1

Conclusions

Lower admission LVOT-VTI was an independent determinant of worse clinical outcomes in hospitalized HFpEF patients, indicating that LVOT-VTI on admission could be a useful marker for risk stratification in these patients.

Expression of Monocarboxylate Transporter 1 in Oral and Ocular Canine Melanocytic Tumors

Solid tumors are composed of a heterogeneous population of cells surviving in various concentrations of oxygen. In a hypoxic environment, tumor cells generally up-regulate glycolysis and, therefore, generate more lactate that must be expelled from the cell through proton transporters to prevent intracellular acidosis. Monocarboxylate transporter 1 (MCT1) is a major proton transporter in mammalian cells that transports monocarboxylates, such as lactate and pyruvate, together with a proton across the plasma membrane. Melanocytic neoplasia occurs frequently in dogs, but the prognosis is highly site-dependent. In this study, 50 oral canine melanomas, which were subdivided into 3 histologic subtypes, and 17 ocular canine melanocytic neoplasms (14 melanocytomas and 3 melanomas) were used to examine and compare MCT1 expression. Immunohistochemistry using a polyclonal chicken anti-rat MCT1 antibody showed that most oral melanoma exhibited cell membrane staining, although there were no significant differences observed among the 3 histologic subtypes. In contrast, the majority of ocular melanocytic tumors were not immunoreactive. Additionally, we documented the presence of a 45-kDa band in cell membrane protein Western blots, and sequencing of a reverse transcriptase polymerase chain reaction band of expected size confirmed its identity as a partial canine MCT1 transcript in 3 oral tumors. Increased MCT1 expression in oral melanomas compared with ocular melanocytic tumors may reflect the very different biology between these tumors in dogs. These results are the first to document canine MCT1 expression in canine tumors and suggest that increased MCT1 expression may provide a potential therapeutic target for oral melanoma.

Significance of caveolin-1 and matrix metalloproteinase 14 gene expression in canine mammary tumours

Canine mammary tumours (CMTs) are the most common neoplasms affecting female dogs. There is an urgent need for molecular biomarkers that can detect early stages of the disease in order to improve accuracy of CMT diagnosis. The aim of this study was to examine whether caveolin-1 (Cav-1) and matrix metalloproteinase 14 (MMP14) are associated with CMT histological malignancy and invasion. Sixty-five benign and malignant CMT samples and six normal canine mammary glands were analysed using quantitative reverse transcription-polymerase chain reaction. Cav-1 and MMP14 genes were highly expressed in CMT tissues compared to normal tissues. Cav-1 especially was overexpressed in malignant and invasive CMT tissues. When a CMT cell line was cultured on fluorescent gelatin-coated coverslips, localisation of Cav-1 was observed at invadopodia-mediated degradation sites of the gelatin matrix. These findings suggest that Cav-1 may be involved in CMT invasion and that the markers may be useful for estimating CMT malignancy.

Monocarboxylate transporter 1 (MCT1) in the liver of pre-ruminant and adult bovines

This study investigated the distribution and expression of monocarboxylate transporter 1 (MCT1) in the livers of pre-ruminant calves and adult bovines (bulls and cows), using different molecular biological techniques. Reverse transcription-polymerase chain reaction (RT-PCR) verified the presence of mRNA encoding for MCT1 in both pre-ruminant and adult bovine livers. Immunohistochemically, MCT1 was clearly demonstrated on the sinusoidal surfaces of bovine hepatocytes but its expression varied widely between pre-ruminants and adult bovines. In pre-ruminants, a faint hepatocellular expression of MCT1 was observed in a few hepatocytes, whereas an intense immunoreactive staining for MCT1 was shown in the majority of adult bovine hepatocytes. Western blot analysis also confirmed the results of the immunohistochemistry. Quantitative immunoblotting, as estimated by densitometric analysis, showed that the level of MCT1 in the liver of adult bovines was 8-9-fold greater (P<0.01) than that in pre-ruminant calf livers although no significant differences were detected between bulls and cows. The results demonstrated that MCT1 may play a crucial role in the transport of propionate in bovine liver, suggesting that MCT1 expression may be influenced by developmental and metabolic regulations.

Monocarboxylate transporter 1 gene expression in the ovine gastrointestinal tract

In this study, we investigated the tissue distribution and expression of monocarboxylate transporter 1 (MCT1) along the gastrointestinal tract of sheep. Western blot analysis suggested the presence of MCT1 as a 43-kDa protein in immunoblots of membranes from the various tissues examined. The results of Western blotting were further confirmed by immunohistochemical studies, which revealed intense immunoreactivity for the MCT1 protein in the forestomach (rumen, reticulum and omasum) and large intestine (caecum, proximal and distal colon). Moderate reactivity, however, was detected in the abomasum, while no immunoreactivity could be seen in any regions of the small intestine examined. Furthermore, MCT1 was expressed at the mRNA level as determined by reverse transcriptase polymerase chain reaction (RT-PCR), which showed a band of the expected size (300 bp) in all tissues examined. From these results we concluded that MCT1 protein is highly expressed and distributed in the stomach and large intestine of sheep suggesting that MCT1 may play a significant role in the transport of short chain fatty acids and their metabolites in the gastrointestinal tract of ruminants.

Expression and distribution of monocarboxylate transporter 1 (MCT1) in the gastrointestinal tract of calves

In the present study the expression and distribution of monocarboxylate transporter 1 (MCT1) along the gastrointestinal tract (rumen, reticulum, omasum, abomasum, duodenum, jejunum, ileum, cecum and colon) of calves were investigated on both mRNA and protein levels. The expression of MCT1 protein and its distribution were determined by Western blotting and immunohistochemical staining, respectively by using antibody for MCT1. MCT1 protein was visualized as a 43-kDa band on immunoblots of the membrane proteins prepared from the various regions examined, and it was more highly expressed in forestomach and large intestine than in abomasum and small intestine. With the use of reverse transcriptase-polymerase chain reaction, mRNA encoding for MCT1 was demonstrated in the different tissues examined. The immunohistochemical study confirmed the Western blot findings and showed strong MCT1 immunopositive staining in the stratified squamous epithelia of the forestomach as well as the epithelial cells lining the digestive tract in the cecum, proximal colon, and distal colon. The results suggest that MCT1 may play a role in the transport of SCFA and their metabolites in the gastrointestinal tract of bovines.

Analysis of cytokines in the early development of gastric secondary lymphoid follicles in Helicobacter pylori-infected BALB/c mice with neonatal thymectomy

Immunological interaction between the host and Helicobacter pylori seems to play a critical role in follicular formation in gastric mucosa. We reported H. pylori-induced follicular gastritis model using neonatally thymectomized mice. In this study, we investigated the involvement of various cytokines in this model. BALB/c mice were thymectomized on the third day after birth (nTx). At 6 weeks old, these mice were orally infected with H. pylori. Histological studies showed that follicular formation occurred from 8 weeks after the infection and that most of the infiltrating lymphocytes were CD4(+) and B cells. Neutrophils increased transiently at 1 week after the infection. Gamma interferon, interleukin-7 (IL-7), and IL-7 receptor were expressed in the stomach of the nTx mice irrespective of the infection. In contrast, expressions of the tumor necrosis factor alpha, IL-4 and lymphotoxin-alpha genes were remarkably upregulated by the infection. Our findings suggest that follicular formation may require cooperative involvement of a Th2-type immune response, tumor necrosis factor alpha and lymphotoxin-alpha in addition to the Th1-type immune response in H. pylori-induced gastritis in nTx mice.

cDNA cloning and expression of a bovine phenol UDP-glucuronosyltransferase, BovUGT1A6

A full-length cDNA encoding a phenol UDP-glucuronosyltransferase was isolated by plaque hybridization, RT-PCR and 5'-RACE from a cDNA library prepared from the bovine liver. The deduced amino acid sequence (529 amino acid residues) has A signal sequence (23 amino acid residues) at the amino terminus and a transmembrane-anchoring domain (17 amino acid residues) at the carboxyl terminus. The encoded protein has a potential asparagine-linked glycosylation site (Asn291). The cloned cDNA was named bovUGT1A6 on the basis of the amino acid similarity. BovUGT1A6 cloned in the pAAH5 expression vector was transformed into Saccharomyces cerevisiea AH22 cells to obtain an active 54-kDa bovUGT1A6 enzyme. The expressed enzyme represented UDP-glucuronosyltransferase activities toward 1-naphthol and 4-methylumbelliferone, confirming that the isolated cDNA is an isoform of bovine phenol UDP-glucuronosyltransferase. Microsomal UDP-glucuronosyltransferase activity toward 1-naphthol in the bovine kidney cortex was found to be higher than that in the liver and other organs, and mRNA of bovUGT1A6 was more strongly detected in the kidney on Northern blotting analysis. These results suggest that the bovine kidney, which strongly expresses bovUGT1A6, is a significant organ for xenobiotics glucuronidation.

Smooth muscle layer-dependent distribution of 5-hydroxytryptamine(7) receptor in the porcine myometrium

1. To analyse the mechanisms of muscle layer-dependent inhibition of porcine myometrial contractility by 5-hydroxytryptamine (5-HT), the effects of 5-HT, 5-carboxamidotryptamine(5-CT), 5-methoxytryptamine (5-MeOT), forskolin and cyclic adenosine 3', 5'-monophosphate (cyclic AMP) analogues on spontaneous and stimulant-induced contractions were examined in longitudinal (LM) and circular muscles (CM). In addition, accumulation of cyclic AMP by 5-HT and distribution of 5-HT(7) receptors in LM and CM layers were compared using biochemical and molecular approaches. 2. 5-HT receptor agonists inhibited the spontaneous contractions of LM and CM (5-CT>5-HT>5-MeOT), but CM was more sensitive than was LM. The inhibition by the agonists was antagonized by methiothepin (100 nM). 3. Carbachol-, high-K(+)-, histamine- and Ca(2+)-induced contractions were inhibited by 5-HT with different responses (CM>LM). Even in the presence of 3-isobutyl-1-methylxanthine (IBMX), the inhibition by 5-HT in the CM was still more conspicuous than that in the LM. 4. Compared with the CM, the inhibition of spontaneous contraction by forskolin, dibutyryl-cyclic AMP and 8-bromo-cyclic AMP was marked in the LM. 5. 5-HT (1 nM - 1 microM) increased the cyclic AMP in both muscle layers, but the increment in the CM was higher than that in the LM whether IBMX was present or not. 6. LM and CM layers contained a single class of [(3)H]-5-CT binding sites with a similar K(d) value (0.21 - 0.24 nM). However, B(max) (5-HT(7) receptor concentration) in the CM (120.6 fmol mg(-1) protein) was higher than that in the LM (30.4 fmol mg(-1) protein). 7. The molecular study (reverse transcription polymerase chain reaction) demonstrated the expression of 5-HT(7) receptor mRNA in the CM was higher than that in the LM. 8. These results suggest that the muscle layer-dependent difference in inhibition by 5-HT is not restricted to spontaneous contraction but applies to various contractions in the porcine myometrium. Different inhibition of the contractility by 5-HT is caused by muscle layer-related accumulation of cyclic AMP (CM>LM), due to smooth muscle-layer dependent distribution (CM>LM) of 5-HT(7) receptors.

Nosema tyriae n.sp. and Nosema sp., microsporidian parasites of Cinnabar moth Tyria jacobaeae

Nosema tyriae n.sp. was found in 63% of a population of Cinnabar moth larvae (Tyria jacobaeae). The infection was found in the gut wall, silk glands, and fat body and was probably generalized but appeared to be of low pathogenicity. Merogony and sporogony were by binary fission of diplokaryotic stages. Fresh spores were elongate, slightly pointed at the anterior end, and measured 4.7 x 2.0 microm. Ultrastructural features of special interest were 20-nm tubules connecting the surface of sporonts with host cell cytoplasm and, in the spores, a deeply domed polar sac, polaroplast consisting of closely packed longitudinally arranged membranes and loosely packed horizontally arranged membranes, and 10.5-14 coils of the polar tube in a single rank. The 16S rRNA genes of N. tyriae and Nosema bombycis from silkworms, Bombyx mori, differed by only six nucleotides and N. tyriae spores gave a moderately positive reaction with a monoclonal antibody raised to N. bombycis. N. tyriae was infective to B. mori but was less virulent than N. bombycis. However, no amplification product was obtained by PCR using N. tyriae DNA and primers considered to be specific for N. bombycis. Also, the spores of the two species are of entirely different shapes. A second diplokaryotic microsporidium, Nosema sp., found as a light infection in only one of the larvae had much smaller developmental stages and spores measuring 3.8 x 2.0 microm (fixed). Ultrastructurally it was distinguished by an abundance of dense membranes in cytoplasmic vesicles in both meronts and sporonts. Spores with up to 15 coils of the polar tube in irregular clusters or with about 12 coils in a single rank were observed in the tissues fixed from the one larva infected with this parasite. As this larva had been kept with N. tyriae-infected larvae for a few days before examination, it is possible that the two types of spores resulted from a double infection.

Glucuronidation of the environmental oestrogen bisphenol A by an isoform of UDP-glucuronosyltransferase, UGT2B1, in the rat liver

Bisphenol A, an environmental oestrogenic chemical, was found to conjugate highly with glucuronic acid in male rat liver microsomes studied in vitro. In the various isoforms tested (1A1, 1A3, 1A5, 1A6, 1A7 and 2B1), glucuronidation of bisphenol A and of diethylstilboestrol, a synthetic crystalline compound possessing oestrogenic activity and known to be glucuronidated by liver microsomes, was catalysed by an isoform of UDP-glucuronosyltransferase (UGT), namely UGT2B1, which glucuronidates some endogenous androgens. UGT activity towards bisphenol A in liver microsomes and in UGT2B1 expressed in yeast AH22 cells (22.9 and 0.58 nmol/min per mg of microsomal proteins respectively) was higher than that towards diethylstilboestrol (75.0 and 4.66 pmol/min per mg of microsomal proteins respectively). UGT activities towards both bisphenol A and diethylstilboestrol were distributed mainly in the liver but were also observed at substantial levels in the kidney and testis. Northern blot analysis disclosed the presence of UGT2B1 solely in the liver, and about 65% of the male rat liver microsomal UGT activities towards bisphenol A were absorbed by the anti-UGT2B1 antibody. These results indicate that bisphenol A, in male rat liver, is glucuronidated by UGT2B1, an isoform of UGT.

The significance of amino acid residue Asp446 for enzymatic stability of rat UDP-glucuronosyltransferase UGT1A6

Asp446 in rat UDP-glucuronosyltransferase (UGT), UGT1A6, is an essential amino acid residue for its enzymatic activity (H. Iwano et al. Biochem. J. 325, 587-591, 1997). The role of Asp446 in UGT1A6 was investigated by comparing some properties of UGT mutant proteins that have a single mutation (D446K, D446E, D446N, D446Q, D446A, and D446T). These mutants, except D446K, had catalytic activities toward 1-naphthol and 4-methylumbelliferone. The UGT activities of D446E and D446N were about half of that of the wild type, and the activities of the other mutants were only about 1/5-1/10 of that of the wild type. The Km values for 1-naphthol of these mutants were similar to that of the wild type, while the values for UDP-glucuronic acid were slightly higher. The mutants were unstable in a low-pH buffer solution and were dramatically inactivated by heat treatments. Interestingly, after 30 min of treatment at 37 degrees C in the presence of UDP-glucuronic acid, the UGT activities of all functional mutants were elevated. These results suggest that Asp446 is an indispensable residue for folding a functional conformation of rat UGT1A6 by cooperation with UDP-glucuronic acid.

UDP-glucuronosyltransferase UGT1A7 induced in rat small intestinal mucosa by oral administration of 2-naphthoflavone

In the rat intestine, UDP-glucuronosyltransferase (UGT) isoforms were highly induced by oral administration of 2-naphthoflavone, as shown by intestinal UGT activity toward 1-naphthol (1-NA). The greatest increase in UGT activity occurred in the duodenum. Using UGT1A6 cDNA as a probe, we obtained three types of clones corresponding to UGT1A2, UGT1A6 and UGT1A7, in a ratio of 1:1:8, from a cDNA library constructed from the 2-naphthoflavone-treated rat intestine. The induction of each isoform was evaluated by means of Northern blotting with isoform-specific probes. The mRNAs of UGT1A6 (glucuronizing various phenolic xenobiotics) and the mRNAs of UGT1A7 (glucuronizing the ultimate carcinogenic metabolite of benzo(a)pyrene) were expressed constitutively and were highly induced in the duodenum and proximal jejunum. S1 mapping showed that induction of the isoforms of the UGT1 family was more pronounced in the liver than in the small intestine and that UGT1A7 was the major UGT1 isoform in the small intestine of vehicle-treated rats and in that of 2-naphthoflavone-treated rats. These results indicate that, in rats, UGT1A7 is expressed constitutively and is particularly inducible in the small intestine. In the light of these results, we believe that the UGT1A7 isoform would play an important role in glucuronidation in the small intestinal mucosa of rats.

Inhibitory effects of uridine diphosphate on UDP-glucuronosyltransferase

Inhibitory effects of uridine diphosphate on the enzymatic activity of UDP-glucuronosyltransferase (UGT) were investigated. Pyrimidine nucleotides such as UDP, UTP and cytidine diphosphate reduced the activity of rat purified UGT (phenol UGT) to about 10%, 48% and 46% of the control, respectively, at the same concentration as a donor substrate, UDP-glucuronic acid. Purine nucleotides, uridine monophosphate, glucuronic acid and some UDP-sugars were only slightly inhibitory toward the transferase. Similar effects were observed in the expressed UGT (UGT1A6; corresponding to phenol UGT) in yeast cells and rat liver microsomal membrane-binding UGT, indicating that uracil and diphosphate residues are essential for the UDP inhibition. Interestingly, 2'-deoxy UDP was found to be a less effective inhibitor (about 50% inhibition) than UDP on the purified, the expressed (UGT1A6 and UGT2B1) and microsomal membrane-binding UGTs. These results indicate that not only uracil and diphosphate residues but also 2'-hydroxyl residue of UDP ribose participates in the interactions between UDP and UDP-glucuronosyltransferase.

High induction of phenol UDP-glucuronosyltransferase in the kidney medulla of beta-naphthoflavone-treated rats

Phenol UDP-glucuronosyltransferase activity was highly induced in the microsomes of the kidney medulla of rats by beta-naphthoflavone treatment. In the medulla, phenol UDP-glucuronosyltransferase and its mRNA were greatly increased in both immunoblotting and Northern blot analyses following beta-naphthoflavone treatment of the rats. In untreated rat kidneys, phenol UDP-glucuronosyltransferase was detected by immunohistochemical analysis only in proximal convolution tubular cells located in the cortex. After beta-naphthoflavone treatment of the rats, UDP-glucuronosyltransferase appeared in the epithelial cells in the straight portion of the distal tubules located in the medulla. In conclusion, the medullary distal tubular cells have high latent glucuronidation activity and are thought to play an important role in drug excretion.

A critical amino acid residue, asp446, in UDP-glucuronosyltransferase

An amino acid residue, Asp446, was found to be essential for the enzymic activity of UDP-glucuronosyltransferase (UGT). We obtained a rat phenol UGT (UGT1*06) cDNA (named Ysh) from male rat liver by reverse-transcription (RT)-PCR using pfu polymerase. A mutant Ysh having two different bases, A1337G and G1384A (named Ysh A1337GC1384A), that result in two amino acid substitutions, D446G and V462M, was obtained by RT-PCR using Taq polymerase. Ysh was expressed functionally in microsomes of Saccharomyces cerevisiae strain AH22. However, the expressed protein from YshA1337GG1384A had no transferase activity. Two other mutant cDNAs with YshA1337G having one changed base, A1337G, resulting in one amino acid substitution, D446G, and YshG1384A having a changed base, G1384A, resulting in an amino acid substitution, V462M, were constructed and expressed in the yeast. The expressed protein from YshG1384A (named YshV462M) exhibited enzymic activity, but the one from YshA1337G (named YshD446G) did not show any activity at all. Asp446 was conserved in all UGTs and UDP-galactose:ceramide galactosyltransferases reported, suggesting that Asp446 plays a critical role in each enzyme.

Effects of discrimination learning on the rat striatal dopaminergic activity: a microdialysis study

The prefrontal cortex (PFC) has anatomical and functional relationships with the striatum. In a previous study we showed that dopamine (DA) turnover in the PFC of rats is enhanced during the performance of a discrimination task. In the present study, we used an in vivo microdialysis method to examine whether DAergic activity in the striatum could also be altered by the discrimination task. The results showed a substantial and sustained suppression of DAergic activity during and after the discriminative behaviour. The fact that the discriminative performance induced opposite changes in DAergic activity in the striatum and the PFC is consistent with the results of biochemical studies, suggesting that the suppressed DA turnover in the striatum may be induced by the enhanced DAergic activity in the PFC during the discrimination task.

Acetylcholine in the hippocampus during the discrimination learning performance in a rat model of chronic cerebral ischaemia

Acetylcholine (ACh) release in the hippocampus of Wistar strain rats with permanent bilateral occlusion of the common carotid arteries was examined during a discrimination learning task using a microdialysis method. Such occlusion resulted in obvious impairment of the discrimination performance. The state, the basal value and released patterns, of ACh in the hippocampus differed in the sham-operated control and the experimental group, while ACh release was elevated during the dialysis experiment in both groups. These findings suggested that the bilateral occlusion produced persistent learning deficits from an early stage after the operation and that the impaired discrimination learning performance might be related to the diffusion of ACh in the hippocampus.

Septo-hippocampal cholinergic system under the discrimination learning task in the rat: a microdialysis study with the dual-probe approach

To investigate regulation of the septo-hippocampal cholinergic system by dopaminergic inputs to the septum in rats which performed a discrimination learning task, an in vivo microdialysis method with the dual-probe approach was used. Rats were trained to discriminate between lamp-on and -off states under an operant-type learning procedure. After stable discriminative behavior was established, dialysis probes were implanted into the hippocampus and the lateral septum area of each rat. The concentration of dopamine (DA) in the septum rapidly increased within 20 min after the beginning of a learning session. However, another group of rats trained on a similar but non-discriminative task showed no such increase. The concentration of acetylcholine (ACh) in the hippocampus was significantly enhanced during the learning session and rapidly returned to the basal value after the session, but showed a delayed and diminished increase in the non-discrimination group. These results suggest that DAergic inputs to the septum may be involved in control of the septo-hippocampal cholinergic system which is of importance for discrimination learning behavior.

The relationship between learning performance and dopamine in the prefrontal cortex of the rat

To clarify the relationship between dopamine (DA) release in the prefrontal cortex and learning performance, extracellular DA was measured by an in vivo microdialysis method during a discrimination learning task. Rats were trained to discriminate between lamp-on and -off states under an operant-type learning procedure. After stable discriminative behavior was established, a microdialysis experiment was conducted. Inverse relationships were seen between the relative ratio of DA after the beginning of a learning session to the basal level and the responses (total, correct and error responses) during a session. The results indicate that the degree of DA release in the prefrontal cortex is involve in the inhibitory mechanism of the response during discrimination learning performance.