Serial changes in plasma brain natriuretic peptide concentration at the infarct and non-infarct sites in patients with left ventricular remodelling after myocardial infarction.

OBJECTIVES: To clarify the role of infarct and non-infarct sites on left ventricular (LV) remodelling after myocardial infarction by measuring brain natriuretic peptide (BNP) from each site. METHODS AND RESULTS: BNP from the aorta and the anterior interventricular vein (AIV) was measured in 45 patients with first anterior myocardial infarction at one, six, and 18 months. The LV was significantly dilated (> 10 ml/m(2) of end diastolic volume from one to 18 months) in 20 patients (remodelling (R) group) but not in 25 others (non-remodelling (NR) group). Patient characteristics and LV functions did not differ significantly at one month but plasma BNP concentration was higher in group R than in group NR (336 (288) v 116 (106) pg/ml, p < 0.01), predicting the degree of LV dilatation. The difference in BNP concentration between the aortic root and AIV (DeltaBNP), reflecting BNP secreted from the infarct site, did not differ at one month. In both groups BNP and DeltaBNP significantly decreased from one to six months (p < 0.05) and decreased from six months to 18 months, but the change was not significant. BNP and DeltaBNP were significantly higher in group R than in group NR after six months, when LV dilatation was not evident in both groups. CONCLUSION: Enhanced BNP secretion at one month in the non-infarct and infarct ventricular sites predicts subsequent LV dilatation (that is, remodelling). The slower process of LV remodelling decreased BNP secretion at both sites. Thus, BNP concentration should be useful for monitoring ventricular remodelling after infarction.

Prolonged diastolic dysfunction following exercise induced ischaemia: a gated myocardial perfusion SPECT study.

Prolonged impairment of left ventricular (LV) systolic function following exercise induced ischaemia has been well demonstrated. The objective of this study was to examine the effect of exercise induced ischaemia on the post-stress LV diastolic function in patients with coronary artery disease (CAD). Seventy-four subjects with known or suspected CAD underwent gated myocardial single photon emission computed tomography (SPECT) 1 h after administration of 99mTc tetrofosmin according to a standard same day exercise rest protocol. LV volumes and ejection fractions (LVEFs) were determined by the Cedars-Sinai program. Fourier transformation of the gated SPECT volume curve was performed retaining the fourth order harmonics, and peak filling rate (PFR) and time-to-PFR (TPFR) were calculated from the derivative curve. In patients with exercise induced ischaemia (n =26), 1 h post-stress PFR (2.66+/-0.75 s(-1)) and TPFR (119+/-12 ms) were significantly impaired in comparison to the resting PFR (3.06+/-0.74 s; P=0.0002) and TPFR (114+/-10 ms; P=0.03), respectively. In normal subjects (n =26) and in patients with infarction (n =22), the post-stress indices were similar to the resting values. When reduction of PFR or LVEF greater than the variability (2SD) of differences between the post-stress and resting values in the normal group was defined as significant impairment, six of the 26 ischaemic patients (23%) had such changes in PFR. All these patients exhibited severe ischaemia and five of them had simultaneous systolic impairment. Only one (4%) of the normal subjects and none of the patients in the infarction group showed such impairments. Stepwise logistic regression analysis of stress, scan and coronary variables revealed that the summed reversibility score, a scintigraphic index of ischaemic severity, was the only determinant of post-stress changes in LVEF and PFR. In conclusion, exercise induced LV diastolic impairment persists for a prolonged period after resolution of the ischaemic episode. The incidence and magnitude of the diastolic impairment are determined by the severity of the exercise provoked ischaemia.

14 C-deoxyglucose imaging overestimates myocardial viability in subacute infarction of rats.

Clinical studies using 18F-fluorodeoxyglucose suggest that this tracer may overestimate myocardial viability. This study aimed to elucidate whether 2-deoxyglucose accurately indicates myocardial viability at the early phase of myocardial infarction. Autoradiography with 14C-deoxyglucose was performed in fasting rats whose left coronary artery was occluded for 60 min and then reperfused. 14C-deoxyglucose was injected 30 min after the reperfusion (acute; n=10) or 1 week later (subacute; n=9). Infarction and risk areas were identified by triphenyl tetrazolium chloride or haematoxylin-eosin staining and methylene blue, respectively. Immuno-histochemical staining using anti-glucose transporter 1 and 4 antibodies was performed. At the acute stage, the uptake of deoxyglucose was consistent with the grade of anti-glucose transporter 4 expression. At the subacute stage, the uptake of deoxyglucose in poorly viable myocardium (543.4+/-343.7%: normalized with the uptake at the right ventricle) as well as in the viable one (335.2+/-149.8%) in the risk area was significantly greater than that in the remote area (116.4+/-94.9%, P<0.01). Anti-glucose transporter 1 was expressed in the poorly viable area where inflammatory cells infiltrated. It is concluded that deoxyglucose uptake by inflammatory cells which express anti-glucose transporter 1 causes overestimation of myocardial viability at subacute stage.

Prognostic significance of cardiac (123)I metaiodobenzylguanidine imaging for mortality and morbidity in patients with chronic heart failure: a prospective study.

OBJECTIVE: To determine whether cardiac iodine-123 metaiodobenzylguanidine ((123)I MIBG) imaging is useful in predicting the prognosis of patients with chronic heart failure. DESIGN: Cardiac (123)I MIBG imaging was done on entry to the study. The cardiac MIBG washout rate was calculated from anterior chest view images obtained 20 and 200 minutes after injection of the isotope. Study patients were divided into two groups with washout rates above and below 27% (the mean value + 2 SD obtained in 20 normal subjects), and were then followed up. SETTING: Tertiary referral centre. PATIENTS: 79 patients with chronic heart failure in whom the left ventricular ejection fraction was less than 40%. RESULTS: There were 37 patients in group 1 (washout rate of >/= 27%) and 42 in group 2 (< 27%). During a follow up period of between 1 and 52 months, eight patients died suddenly and five died of worsening heart failure in group 1, while none died in group 2; 13 patients in group 1 and four in group 2 were admitted to hospital for progressive heart failure. Kaplan-Meier analysis showed that group 1 had a significantly higher mortality and morbidity (p = 0.001 and p < 0.001, respectively) than group 2. CONCLUSIONS: Cardiac (123)I MIBG washout rate seems to be a good predictor of prognosis in patients with chronic heart failure.

Dynamic viewer of medical events in electronic medical record.

Medical record should enable doctors to comprehend the patient's history and select suitable medical treatment. In paper based medical records, medical events (examination, treatment etc.) are recorded successively, and problem oriented recording is difficult to be applied to patients with much information and a long history. Consequently it is not easy to understand the patient's history from paper based medical records. In order to solve this problem, we developed the flow sheet system in our electronic medical record (EMR). To make a flow sheet, we analyzed the structure of the medical event data. In this paper we introduced the medical event information model for our EMR. Furthermore, we clarified the specification of the data presentation on the flow sheet. We developed the flow sheet on the basis of these analyses. Because there are 3 layers in the vertical axis of the flow sheet, many items of the medical event can be displayed on the screen. When user clicks the cell, the corresponding detail data including images are shown. This system functions to link medical event items with a problem, and shows the bundled items on the flow sheet when the user selects the problem. We implemented this system in Osaka University Hospital. The number of the types of medical events and those of detail events in inpatients are 5.0+1.7 (mean+SD) and 60+47, respectively. The medical doctors in Osaka University Hospital evaluated this system, and concludes that the flow sheet data presentation makes comprehension of the patient's history easier than paper based records. As to the function of bundling the items relevant to the problem, they feel it is especially useful for patients with chronic disease. Thus the flow sheet data presentation in EMR is useful for medical practice.

Troglitazone enhances glucose uptake induced by alpha-adrenoceptor stimulation via phosphatidylinositol 3-kinase in rat heart.

1. Thiazolidinedione-derived agents have been reported to act as insulin sensitizers by augmenting insulin-dependent stimulation of phosphatidylinositol 3-kinase (PI3K) activity in a specific manner. It has been suggested that alpha-adrenoceptor stimulation mediates glucose uptake through PI3K in the heart. 2. To elucidate whether the thiazolidinedione-derived agent troglitazone (TRO) affects glucose uptake induced by alpha-adrenoceptor stimulation through PI3K, the rate of glucose uptake was quantified from the rate of accumulation of sugar phosphate (d[SP]/dt) using [(31)P] nuclear magnetic resonance spectroscopy after substitution of glucose with 2-deoxyglucose in rat perfused heart. Hearts were stimulated with 100 micromol/L phenylephrine plus 10 micromol/L propranolol (alpha-adrenoceptor stimulation), or 1 micromol/L isoproterenol plus 10 micromol/L phentolamine (beta-adrenoceptor stimulation). 3. The d[SP]/dt in the alpha- and beta-adrenoceptor-stimulated groups (0.45 +/- 0.06 and 0.42 +/- 0.04 micromol/min per g, respectively) was higher than that of the control group (0.27 +/- 0.02 micromol/min per g; P < 0.01). The addition of 2 microg/mL troglitazone to alpha-adrenoceptor stimulation augmented d[SP]/dt (0.72 +/- 0.08 micromol/min per g; P < 0.05 vs the alpha-adrenoceptor-stimulated group), which was effectively blocked by 3 micromol/L wortmannin (0.35 +/- 0.06 micromol/min per g; P < 0.01 vs troglitazone + alpha-adrenoceptor stimulation group). However, addition of troglitazone to beta-adrenoceptor stimulation did not alter d[SP]/dt (0.33 +/- 0.02 micromol/min per g; P = NS vs the beta-adrenoceptor-stimulated group). 4. These results indicate that troglitazone acutely enhances alpha-adrenoceptor stimulation on glucose uptake through a PI3K-dependent pathway, thus possibly improving glucose utilization in a catecholamine-released state.

Abnormal myocardial free fatty acid utilization deteriorates with morphological changes in the hypertensive heart.

The left ventricle's morphological adaptation to high blood pressure is classified into 4 patterns based on mass and wall thickness. The geometric changes caused by maladaptation to pressure overload possibly relate to progression of contractile dysfunction with abnormal energy metabolism. The present study assessed whether the geometric adaptation of the left ventricle (LV) to high blood pressure relates to changes in myocardial energy metabolism, especially free fatty acid (FFA) utilization. Thirty-five patients with essential hypertension underwent echocardiography and dual isotopes myocardial scintigraphy using iodine-123 labeled 15-p-iodophenyl-3-(R,S)-methylpentadecanoic acid (BMIPP, an analogue of a FFA) and thallium-201 (Tl-201). Systolic (endocardial fractional shortening; %FS) and diastolic indices (the ratio of early to atrial filling waves; E/A) of LV function were also assessed. Quantitative myocardial BMIPP uptake was evaluated by the BMIPP/TI-201 myocardial uptake ratio (B/T). The subjects were divided into 4 groups based on LV mass and wall thickness: (1) concentric hypertrophy (CH), (2) eccentric hypertrophy (EH), (3) concentric remodeling (CR), and (4) normal geometry (N). The %FS was lower in the EH group than in the other groups. The mitral E/A ratio in the CH group was lowest. B/T was significantly decreased in the EH group compared with the N group (p < 0.05). B/T correlated with the mitral E/A ratio significantly (p < 0.05, r = 0.42), whereas there was no relationship between %FS and B/T. These results indicate that the geometric changes occurring in hypertensive hearts strongly correlate with alternations in cardiac function and with abnormal myocardial FFA metabolism, and that the latter is associated with diastolic abnormality, but not with systolic function.

Intracellular calcium level required for calpain activation in a single myocardial cell.

We have hypothesized that calpain mediates myocardial injury induced by Ca(2+)overload. However, in vitro study demonstrated that the calcium requirement for calpain activation is around 10 microm, which is difficult to reach without the cell collapsing. Furthermore, because calpastatin is abundant in the myocardial cell, calpain may not be activated in physiological conditions. To elucidate whether calpain is activated by the calcium concentration reachable in myocardial living cells, we measured the calpain activity and the calcium concentration simultaneously in isolated guinea-pig cardiomyocytes. t-Butoxycarbonyl-Leu-Met-7-amino-4chlorimethylcoumarin (Boc-Leu-Met-CMAC), a fluorescent substrate of calpain, and/or fura red, a calcium indicator, were loaded into isolated cardiomyocytes together, and their fluorescence were measured separately. Intracellular Ca overload was induced by changing the superfusate from normal Tyrode solution to a sodium-free one. After changing the solution, fluorescence intensity of fura red and Boc-Leu-Met-CMAC did not change for a while, then fluorescence intensity of fura red began to rise. This was followed by the fluorescence intensity of Boc-Leu-Met-CMAC starting to rise 160+/-45 s after [Ca(2+)](i)increase. The relative fluorescence intensity of fura red increased to 1.37+/-0.32 folds of the control at the point that calpain became active. The calcium concentration at this point was estimated as 451 n m. These results indicate that calpain is activated by the slight rise of Ca concentration in intact cardiomyocytes.

Role of intracellular Na(+) kinetics in preconditioned rat heart.

To elucidate the role of intracellular Na(+) kinetics in the mechanism for ischemic preconditioning (IPC), we measured intracellular Na(+) concentration ([Na(+)](i)) using (23)Na-magnetic resonance spectroscopy in isolated rat hearts. IPC significantly delayed the initial [Na(+)](i) increase (d[Na(+)](i)/dt) compared with non-IPC control, resulting in attenuation of Na(+) accumulation (Delta[Na(+)](i)) during 27 minutes of ischemia with better functional recovery. [Na(+)](i) in IPC, but not in control, recovered to preischemic level during a 6-minute reperfusion. The Na(+)-H(+) exchange inhibitor further suppressed d[Na(+)](i)/dt in both control and IPC hearts with concomitant improvement of functional recovery, suggesting little contribution to the mechanism of IPC. The mitochondrial ATP-sensitive K(+) (mito K(ATP)) channel activator diazoxide (30 micromol/L) completely mimicked both [Na(+)](i) kinetics and functional recovery in IPC without any additive effects to IPC. The mito K(ATP) channel blocker 5-hydroxydecanoic acid (100 micromol/L) lost protective effect as well as the attenuation of d[Na(+)](i)/dt and [Na(+)](i) recovery induced by diazoxide. However, 5-hydroxydecanoic acid also lost IPC-induced protection, but incompletely abolished the alteration of d[Na(+)](i)/dt and the [Na(+)](i) recovery. The Na(+)/K(+)-ATPase inhibitor ouabain (200 micromol/L) did not change d[Na(+)](i)/dt in non-IPC hearts, but it abolished the IPC- or diazoxide-induced reduction of d[Na(+)](i)/dt and the [Na(+)](i) recovery, whereas IPC followed by ouabain treatment showed partial functional recovery with smaller Delta[Na(+)](i) than other ouabain groups. In conclusion, alteration of Na(+) kinetics by preserving Na(+) efflux via Na(+)/K(+)-ATPase mediated by mito K(ATP) channel activation mainly contributes to functional protection in IPC hearts. The contribution of mito K(ATP) channel-independent pathway relating to Na(+) kinetics including reduced Na(+) influx is limited in functional protection of IPC.

Proton magnetic resonance spectroscopy of Sjögren-Larsson syndrome heterozygotes.

A deficit of fatty alcohol:NAD+ oxidoreductase complex (FAO) activity has been detected in patients with the Sjögren-Larsson syndrome (SLS). A moderate decrease in FAO activity has also been reported in heterozygote SLS subjects. Abnormal peaks were detected with proton magnetic resonance spectroscopy (1H-MRS) in homozygote SLS subjects. The purpose of this study was to examine whether 1H-MRS can be used to detect metabolic and/or pathological abnormalities in heterozygote SLS subjects. Four SLS heterozygotes were examined using 1H-MRS. A moderate decrease in FAO activity was demonstrated in two of the four heterozygotes. Abnormal peaks were detected at 0.9 ppm in the spectrum from cerebral hemispheres of every heterozygote. 1H-MRS was able to detect an abnormal accumulation of fatty alcohols and lipids, which is expected to increase due to an decrease in FAO activity or dysmyelination in heterozygote SLS subjects. Thus, 1H-MRS is suggested to be a powerful tool in the screening of SLS heterozygotes.

Expression of Epstein-Barr virus in cutaneous T-cell lymphoma including mycosis fungoides.

Cutaneous T-Cell lymphoma (CTCL) is a non-Hodgkin's lymphoma of unknown pathogenesis. Mycosis fungoides (MF) is a clinically determined subset of CTCL with intensive infiltration of lymphoma cells into the epidermis. To determine whether Epstein-Barr virus (EBV) is associated with these lymphoma cells, we performed mRNA in situ hybridization in 5 cases of CTCL and 7 cases of MF using an RNA probe transcribed from BamHI W fragment of EBV genome. These transcripts were detected in the majority of lymphoma cells in all cases examined. We also detected intensive hybridization signals on epidermal squamous cells contiguous to strong infiltration with lymphoma cells into the subcutaneous connective tissue. Similarly, positive signals were detected using the probes transcribed from the sequences of EBV-encoded small nonpolyadenylated RNAs-1 (EBER1) and EBV-determined nuclear antigen-2 (EBNA2). The EBNA2 latent membrane protein-1 (LMP1) and BZLF1 product (ZEBRA) were also detected by immunofluorescence staining using monoclonal antibodies. Further in the same experiment, we detected immunofluorescence of epidermal cells. EBV DNA was detected in all cases tested by DNA in situ hybridization. Moreover, we also identified the signals on epidermal cells via this technique. Polymerase chain reaction revealed amplified EBV DNA for most cases tested. Double staining with immunohistochemistry and RNA in situ hybridization showed that T-cell marker-positive cells, but not EBV-carrying B-cells, exhibited signals for the EB viral RNA. These findings suggest that EBV is involved in the neoplastic transformation of CTCL and MF.

Type IV phosphodiesterase inhibitor suppresses insulin-dependent myocardial glucose uptake.

1. Phosphodiesterase (PDE) IV has been localized at cardiomyocytes and the coronary vasculature and modulates cAMP, but the effect of PDE IV on myocardial glucose uptake has not been demonstrated. 2. Glucose uptake in rat isolated hearts treated with the PDE IV inhibitor rolipram was measured by [31P] nuclear magnetic resonance spectroscopy. 3. Under non-stimulating conditions, glucose uptake was not significantly different between control and rolipram (1 micromol/L)-treated rat hearts, whereas enhanced uptake in insulin-stimulated conditions was significantly attenuated by rolipram. 4. Phosphodiesterase IV inhibitor negatively affects insulin-dependent myocardial glucose uptake.

Transmural heterogeneity of myocardial integrated backscatter in diabetic patients without overt cardiac disease.

It is important to detect early changes in diabetic myocardium, because some diabetic patients suffer from diabetic cardiomyopathy, especially those with poorer glycemic control or hypertension (HT). To clarify whether ultrasonic tissue characterization can noninvasively detect ultrastructural changes in diabetic myocardium, we analyzed the transmural heterogeneity in myocardial integrated backscatter (THIB) in 20 diabetic patients and 16 normal subjects. THIB was defined as the absolute value of difference of integrated backscatter between the endocardial and epicardial half of the myocardium. THIB in diabetic patients was significantly greater than that in normal subjects. In diabetic patients, there was a significant correlation between glycosylated hemoglobin and THIB, and the greater THIB was shown in patients with HT compared with those without HT. Early changes in the myocardium, related to increased interstitial collagen deposition or other occult cardiomyopathic changes, may be detected on the basis of quantitative analysis of THIB in diabetic patients.

Clinical value of lung uptake of iodine-123 metaiodobenzylguanidine (MIBG), a myocardial sympathetic nerve imaging agent, in patients with chronic heart failure.

This study investigated the clinical value of I-123 MIBG pulmonary accumulation and washout in patients with chronic heart failure (CHF). Nineteen patients with CHF and 15 normal volunteers (NL) were included. The uptake ratio of heart to mediastinum (H/M), that of lung fields to mediastinum (L/M), and washout rate (WR) of the heart and lung fields were calculated in anterior planar images and compared with results of echocardiography and cardiac catheterization. In the CHF group, the lung uptake in delayed images increased and lung WR was decreased, suggesting pulmonary endothelial lesions. Furthermore, there was a negative correlation between right and left lung WR and pulmonary arterial diastolic pressure (PA(D)) and pulmonary arterial systolic pressure (PA(s)) in the CHF group. Since the WR of MIBG reflected PA, it may be used as an index of severity of cardiac dysfunction.

Estimation of the area at risk in myocardial infarction of rats by means of I-123 beta-methyliodophenyl pentadecanoic acid imaging.

Clinical investigations have suggested that the defects in SPECT images of a free fatty acid analog, I-123 beta-methyliodophenyl pentadecanoic acid (BMIPP) may indicate the ischemic risk area. To elucidate whether I-123 BMIPP can indicate the area at risk of ischemia, ex-vivo autoradiography was performed in rats whose left coronary artery was occluded for 60 min and then reperfused. I-123 BMIPP was injected at the acute stage (n = 10), or the subacute stage (7 days after reperfusion; n = 9). Infarction and the area at risk were identified by triphenyl tetrazolium chloride staining and injection of methylene blue during religation just before sacrifice, respectively. The BMIPP uptake in the risk area was significantly lower than that in the remote area at the acute (risk, 53.7+/-23.3% of the uptake at right ventricle, mean +/- SD; remote, 109.3+/-11.8%; p < 0.01) and subacute (risk, 52.5+/-11.5%; remote, 97.9+/-14.3%; p < 0.01) stages. In addition, the area with reduced uptake of I-123 BMIPP showed a significant correlation with the area at risk both at the acute (r = 0.98, p < 0.01) and subacute (r = 0.92, p < 0.01) stages. In conclusion, the area at risk can be evaluated by I-123 BMIPP both at the acute and subacute stages.

Changes in perfusion and fatty acid metabolism of rat heart with autoimmune myocarditis.

To elucidate the change in perfusion and aerobic metabolism in myocarditis, tissue counting and dual tracer ex vivo autoradiography with Tl-201 and a free fatty acid analog, I-123- or I-125-labeled (p-iodophenyl)-methyl-pentadecanoic acid (BMIPP), were performed in rats with myocarditis induced by immunization with cardiac myosin. Inflammatory damage was classified histologically. At the acute stage (2-4 weeks after the antigen-injection), total heart uptakes of Tl and BMIPP and the ratio (BMIPP/Tl) were significantly reduced in myocarditis rats (N = 15) compared with the controls (N = 12). Myocardial distribution of Tl and BMIPP was not homogeneous. Relative uptake of Tl and BMIPP (N = 9, 128 regions) was gradually decreased with the extent of inflammation, and the regional BMIPP/Tl was smaller than the control. At the subacute stage (7 weeks after the antigen-injection), total Tl uptake in myocarditis rats (N = 5) recovered to the control level (N = 4), but that of BMIPP was still significantly lower than the control. BMIPP/Tl was still significantly lower in myocarditis. Myocardial distribution of Tl and BMIPP recovered to be more homogeneous. Relative uptake of Tl and BMIPP (N = 6, 78 regions) still gradually but significantly decreased with the extent of inflammation. Regional BMIPP/Tl was still depressed in myocarditis. These results indicate that myocardial perfusion and aerobic metabolism were discrepant and heterogeneously suppressed with severe inflammation during the acute stages, but the difference decreases with time. Examination with Tl-201 and BMIPP may provide information about the severity of myocarditis.

Kinetics of a putative hypoxic tracer, 99mTc-HL91, in normoxic, hypoxic, ischemic, and stunned myocardium.

UNLABELLED: 99mTc-4,9-diaza-3,3,10,10-tetramethyldodecan-2,11-dione dioxime (HL91) was developed as a putative hypoxic reagent. This study focused on the myocardial kinetics of 99mTc-HL91 in various oxygen levels and perfusion states. METHODS: The time-activity curve of 99mTc-HL91 was measured in isolated perfused rat heart after the bolus infusion. RESULTS: 99mTc-HL91 was cleared quickly from normoxic hearts, and retention at 30 min after injection was 0.18 +/- 0.02 percentage injected dose per gram of wet weight (mean +/- SE; n = 6). When the concentration of oxygen bubbling through the perfusate was reduced from 100% to 50%, 20%, 5%, and 0%, retention of 99mTc-HL91 increased to 0.47 +/- 0.03 (n = 5), 0.48 +/- 0.03 (n = 5), 0.71 +/- 0.01 (n = 5), and 0.70 +/- 0.02 (n = 5), respectively (P < 0.05). Compartment analysis revealed that the trapping mechanism, which was dependent on tissue oxygen concentration, determined the retention rate. Although not retained in stunned myocardium (0.17 +/- 0.02, n = 5; P = not significant), 99mTc-HL91 was significantly retained when injected before ischemia (1.06 +/- 0.06, n = 5; P < 0.05). CONCLUSION: These results indicate that retention of 99mTc-HL91 correlates well with oxygen level in the perfusate, suggesting that the agent may be a useful marker of the severity of myocardial hypoxia.

Frequency-dependent changes in calcium cycling and contractile activation in SERCA2a transgenic mice.

OBJECTIVE: This study was undertaken to investigate the mechanism of altered contractility in hearts from transgenic mice overexpressing the sarcoplasmic reticulum (SR) Ca2+ ATPase (SERCA2a). In particular, we sought to determine whether the reported increase in contractility is frequency-dependent, as might be expected if attributable to changes in SR Ca2+ loading. METHODS: Intracellular [Ca2+] and contractile force were measured at room temperature (22 degrees C) simultaneously in fura-2-loaded isometrically-contracting trabeculae dissected from the hearts of FVB/N control (n = 6) or SERCA2a transgenic (n = 6) mice. RESULTS: SERCA transgenics exhibit a positive force-frequency relationship, but this was flat in age- and strain-matched controls. SERCA transgenics exhibit a sizable increase in calcium transient amplitude relative to controls, with a concomitant increase in force generation at higher frequencies of stimulation. Amplitudes of Ca2+ transients (transgenics: 1.56 +/- 0.09 micromol/L, controls: 1.21 +/- 0.14) and twitches (transgenics: 21.71 +/- 0.91 mN/mm2, controls: 13.74 +/- 1.67) were significantly different at 2.0 Hz stimulation (P < 0.05). CONCLUSION: An increase in SERCA expression increases the ability of the sarcoplasmic reticulum to store calcium, such that more calcium is available to be released during each heartbeat at higher stimulation rates.

Detection of viable cortical neurons using benzodiazepine receptor imaging after reversible focal ischaemia in rats: comparison with regional cerebral blood flow.

To elucidate the utility of benzodiazepine receptor imaging for the detection of viable cortical neurons, dual-tracer autoradiography using iodine-125 iomazenil (IMZ) and iodine-123 N-isopropyl-4-iodoamphetamine (IMP) was performed in a model of reversible focal ischaemia during the acute and subacute phases. The right middle cerebral artery of anaesthetized rats was occluded for 60 min using an intraluminal filament and reperfused. In the acute phase study, 125I-IMZ (370 kBq) was injected via the femoral vein at 2 h after reperfusion, and 123I-IMP (37 MBq) was injected at 50 min post-injection. Rats were sacrificed 10 min after the injection of 123I-IMP. In the subacute phase study, the same procedure was performed at 5 days after reperfusion. In the acute phase, the IMP uptake was significantly decreased in almost all areas of the lesioned hemisphere, an exception being the cerebellum; however, the IMZ uptake was significantly decreased only in ischaemic cores. The discrepancy between IMZ and IMP uptake was observed in the lateral neocortex and the lateral caudate putamen (CPu), which were most frequently damaged in this ischaemic model. In the subacute phase, the IMZ uptake in lesioned rats was significantly decreased only in the parietal lobe and hippocampus, though the IMP uptake was decreased in many regions of lesioned hemispheres (the frontal, parietal cortex, CPu, hippocampus and thalamus). Histopathological findings indicated that both the IMP and the IMZ uptake was markedly decreased in necrotic areas. Although the IMP uptake was significantly decreased in the ischaemic areas, the IMZ uptake was maintained in these areas. These results suggest that benzodiazepine receptor imaging is superior to regional cerebral blood flow imaging for the detection of viable cortical neurons in both the acute and subacute phases of ischaemia.