Quantitative assessment of regional myocardial blood flow using oxygen-15-labelled water and positron emission tomography: a multicentre evaluation in Japan

Recently, a method has been proposed for the quantitative measurement of regional myocardial blood flow (MBF) using oxygen-15-labelled water and positron emission tomography (PET). A multicentre project was organized with the intention of evaluating the accuracy of this method, particularly as a multicentre clinical investigative tool. Each of seven institutions performed PET studies on more than five normal volunteers following a specified protocol. The PET study included a transmission scan, a 15O-carbon monoxide static scan and a 15O-water dynamic scan, thereby yielding MBF values which should have been independent of the spatial resolution of the PET scanner employed. Fifty-three subjects (aged 20-63 years, mean+/-SD 36+/-12 years) were studied at rest, and 31 of these subjects were also studied after dipyridamole in five institutions. Inter-institution consistency and intra-subject variation in MBF values were then evaluated. MBF averaged for all subjects was 0.93+/-0.34 ml min(-1) g(-1) at rest and 3.40+/-1.73 ml min(-1) g(-1) after the administration of dipyridamole, and the flow reserve (defined as the ratio of the two MBF values) was 3.82+/-2.12; these values are consistent with previous reports. Resting MBF values were significantly correlated with the heart rate-blood pressure product (RPP) (y=0.31+6.56E-5x, P<0.010), and RPP was in resting MBF observed in all institutions was well explained by the age-dependent RPP. No significant difference was observed in resting MBF among the institutions. Except in one institution, no significant difference was seen in dipyridamole MBF or myocardial flow reserve. No significant difference was found among the myocardial segments. Regional variation was reasonably small in five institutions, but was not acceptable in two institutions, which was attributed to the scanner performance. These observations suggest that the 15O-water PET technique is useful for a multicentre clinical study if the PET scanner can provide time-activity data with good count statistics.

A short peptide derived from the antisense homology box of Fas ligand induces apoptosis in anti-Fas antibody-insensitive human ovarian cancer cells

We found that a short synthetic peptide corresponding to the "antisense homology box" of Fas ligand induced apoptotic cell death of Fas-expressing human ovarian cancer cell lines. The peptide was deduced from residues 256-265 of human Fas ligand, based on the hypothesis that it should contain a specific binding site to the corresponding Fas. Interestingly, the ovarian cancer cell line NOS4, which was sensitive to anti-Fas antibody induced apoptosis, was not affected by the peptide, whereas another cell line, SKOV-3, which was insensitive to anti-Fas antibody, was killed by the peptide. Thus, this short peptide was shown to have a unique activity to induce apoptosis in human ovarian cancer cells in a manner different from anti-Fas antibody.

Antibacterial activity of multiple antigen peptides homologous to a loop region in human lactoferrin

An 11-residue peptide (FQWQRNMRKVR) homologous to just over half the loop region of human lactoferricin is thought to be responsible for antimicrobial properties of human lactoferricin. Multiple antigen peptides (MAP) of the 11-residue peptide exerted significant antibacterial effects against a broad spectrum of bacteria including MRSA. More than eight branching was favourable for increasing its antibacterial activity. Our report shows a novel possibility for MAP to increase the activity of antibiotic peptides other than simply to stimulate antibody production, as reported so far.

Effect of intravenous dipyridamole on cerebral blood flow in humans. A PET study

BACKGROUND AND PURPOSE

Dipyridamole increases the concentration of circulating adenosine, which is a potent vasodilator, by inhibition of uptake of adenosine into the erythrocytes, and hence produces coronary vasodilation. However, the effects of dipyridamole on cerebral circulation is not pronounced. This study investigates the effects of intravenous dipyridamole on cerebral blood flow (CBF) in humans with use of positron emission tomography (PET).

METHODS

In each of 13 healthy subjects, CBF was measured using (15)O-labeled water and PET at rest and during hypercapnia, hypocapnia, and dipyridamole stress; corresponding CBF values were then compared.

RESULTS

CBF values during dipyridamole stress were significantly lower than those measured at rest. The dipyridamole stress PaCO(2) was also significantly lower than the resting PaCO(2). The change in CBF during dipyridamole stress relative to PaCO(2) closely followed the relationship between CBF and PaCO(2) during hypocapnia.

CONCLUSIONS

These results indicate that the observed decrease in CBF during dipyridamole stress was caused by a decrease in PaCO(2) rather than by any direct action of dipyridamole on CBF. The decrease in PaCO(2) during dipyridamole stress was most likely due to hyperventilation, which was a side effect of adenosine. These results support the hypothesis that circulating adenosine is largely prevented from binding to adenosine receptors of cerebral vessels by the blood-brain barrier.

4-hydroxynonenal triggers an epidermal growth factor receptor-linked signal pathway for growth inhibition

Lipid peroxidation has been implicated in the pathogenesis of various diseases. As a major product of membrane lipid peroxidation, 4-hydroxynonenal (HNE) appears after various kinds of oxidative stress, and is known to induce cell growth inhibition. We here analysed the HNE-mediated signal transduction cascade for the growth inhibition of human epidermoid carcinoma A431 cells. HNE dose-dependently induced phosphorylation of multiple cellular proteins including epidermal growth factor receptor (EGFR) in A431 cells, and rapidly upregulated the catalytic actions of EGFR for autophosphorylation and for phosphorylation of casein as an exogenous substrate. Immunoblot analysis by use of HNE-specific antibody demonstrated the binding of HNE to EGFR along with its activation. This binding, which did not induce cross-linking of EGFR, caused a capping of the receptor on the cell surface which mimicked the capping induced by EGF. Phosphorylation and activation of EGFR were followed by phosphorylation of adaptor protein Shc and activation of MAP kinase. Both genistein as a wide spectrum protein tyrosine kinase inhibitor and AG1478 as a specific EGFR tyrosine phosphorylation blocker inhibited activation of EGFR and MAP kinase by HNE. The same inhibitors prevented HNE-mediated growth inhibition, suggesting a close linkage between EGFR/MAP kinase activation and growth inhibition after exposure to HNE. Our results suggest that EGFR may be one of the primary targets of HNE for an oxidative stress-linked cell growth inhibition.

Improvement of impaired myocardial vasodilatation due to diffuse coronary atherosclerosis in hypercholesterolemics after lipid-lowering therapy

BACKGROUND

Diminished myocardial vasodilatation (MVD) in hypercholesterolemics without overt coronary stenosis has been reported. However, whether the diminished MVD of angiographically normal coronary arteries in hypercholesterolemics can be reversed after lipid-lowering therapy is not known.

METHODS AND RESULTS

A total of 27 hypercholesterolemics and 16 age-matched controls were studied. All patients had >1 normal coronary artery, and those segments that were perfused by anatomically normal coronary arteries were studied. Myocardial blood flow (MBF) was measured during dipyridamole loading and at baseline using positron emission tomography and 13N-ammonia, after which MVD was calculated before and after lipid-lowering therapy. Total cholesterol was significantly higher in hypercholesterolemics (263+/-33.8) than in controls (195+/-16.6), and it normalized after lipid-lowering therapy (197+/-19.9). Baseline MBF (ml. min-1. 100 g-1) was comparable among hypercholesterolemics (both before and after therapy) and controls. MBF during dipyridamole loading was significantly lower in hypercholesterolemics before therapy (189+/-75.4) than in controls (299+/-162, P<0.01). However, MBF during dipyridamole loading significantly increased after therapy (226+/-84.7; P<0.01). MVD significantly improved after therapy in hypercholesterolemics (2.77+/-1.35 after treatment [P<0.05] versus 2. 02+/-0.68 before treatment [P<0.01]), but it remained significantly higher in controls (3.69+/-1.13, P<0.01). There was a significant relationship between the percent change of total cholesterol and the percent change of MVD before and after lipid-lowering therapy (r=-0. 61, P<0.05).

CONCLUSIONS

Diminished MVD of anatomically normal coronary arteries in hypercholesterolemics can be reversed after lipid-lowering therapy.

Insulin action on heart and skeletal muscle FDG uptake in patients with hypertriglyceridemia

Abnormal heart and skeletal muscle 18F-fluorodeoxyglucose (FDG) uptake in patients with insulin resistance has been demonstrated. Although the existence of whole-body insulin resistance has been reported in hypertriglyceridemics, its specific role in heart and skeletal muscle FDG uptake in hypertriglyceridemics has not been clarified.

METHODS

We compared heart and skeletal muscle FDG uptake using PET and the whole-body glucose disposal rate (GDR) during insulin clamping in 17 hypertriglyceridemics and 12 age-matched control subjects to increase our knowledge of whole-body insulin resistance and its relationship to heart and skeletal muscle FDG uptake in hypertriglyceridemics.

RESULTS

GDR was significantly reduced in hypertriglyceridemics compared with control subjects (4.50 +/- 1.37 mg/min/kg versus 10.0 +/- 2.97 mg/min/kg, P = 0.00001), as were the skeletal muscle FDG Ki = (k1 x k3)/(k2 + k3) (SFKi: 0.007 +/- 0.003 mL/min/g versus 0.018 +/- 0.01 mL/min/g, P = 0.0001) and skeletal muscle FDG uptake ([SMFU] 0.725 +/- 0.282 mg/min/100 g versus 1.86 +/- 1.06 mg/min/100 g, P = 0.00023). However, myocardial FDG Ki (MFKi) tended to be reduced in hypertriglyceridemics compared with that in control subjects (0.062 +/- 0.017 mL/min/g versus 0.068 +/- 0.015 mL/min/g), but the difference was statistically insignificant (P = 0.3532). Moreover, myocardial FDG uptake (MFU) in hypertriglyceridemics (6.47 +/- 1.72 mg/min/100 g) tended to be reduced compared with that in control subjects (6.97 +/- 1.73 mg/min/100 g), but the difference was statistically insignificant (P = 0.4485). GDR was significantly correlated with SFKi (r = 0.69, P = 0.0022), SMFU (r = 0.612, P = 0.009), MFKi (r = 0.57, P = 0.0174) and MFU (r = 0.505, P = 0.0385) in hypertriglyceridemics.

CONCLUSION

Both heart and skeletal muscle glucose utilization were related to insulin resistance in hypertriglyceridemics. However, the less severe reduction in MFU (compared with SMFU) suggests that myocardium may have a mechanism to oppose insulin resistance in hypertriglyceridemics.

Inhibitory effect on the establishment of hepatic metastasis by transduction of the tissue plasminogen activator gene to murine colon cancer

Hepatic metastasis is a major factor in limiting the prognosis of patients with colon carcinoma. Recent investigations indicate a correlation between plasminogen activator profiles and hepatic metastasis. We examined the effectiveness of tissue plasminogen activator (tPA) gene therapy using a hepatic metastasis model of murine colon carcinoma. Murine colon carcinoma Colon 26 cells transduced with an MFGtPA retroviral vector (Colon 26/tPA) or an MFGLacZ retroviral vector (Colon 26/LacZ) were injected into the liver via the superior mesenteric vein of BALB/c mice, whose survival rates were checked daily. The mean survival rate of mice with hepatic metastasis induced by Colon 26/LacZ was 23.1 days, whereas that of mice with Colon 26/tPA was >100 days. The in vitro proliferation of Colon 26/tPA was comparable with that of Colon 26/LacZ, and antitumor immunity to wild-type Colon 26 cells was not induced after an intrahepatic injection of Colon 26/tPA. We suggest that transduction of the tPA gene to murine colon cancer is useful against the establishment of hepatic metastasis.

Kinetics of oxygen uptake at onset of exercise related to cardiac output, but not to arteriovenous oxygen difference in patients with chronic heart failure

Patients with chronic heart failure performed exercise tests to evaluate the relation of kinetics of oxygen uptake to cardiac output and arteriovenous oxygen difference at the onset of exercise. The kinetics of oxygen uptake are primarily determined by cardiac output; these kinetics are useful in evaluating exercise intolerance and cardiac output response during exercise.

Protein kinase C-dependent anti-apoptotic mechanism that is associated with high sensitivity to anti-Fas antibody in ovarian cancer cell lines

We compared the sensitivities to apoptosis via anti-Fas antibody of two human ovarian cancer cell lines, NOS4 and SKOV-3, both of which strongly express the Fas antigen on their cell surface. Treatment with anti-Fas antibody induced extensive DNA fragmentation in NOS4 cells but none in SKOV-3 cells. However; both cell lines underwent apoptosis in response to calcium ionophore A23187 or sphingomyelinase, demonstrating that the latter cell line is capable of DNA fragmentation. DNA fragmentation was not induced in either cell line by treatment with PKC activator PMA, however treatment with protein kinase C (PKC) inhibitor H-7 induced extensive DNA fragmentation in NOS4 cells, but again none in SKOV-3 cells. Protein kinase A inhibitor HA1004 treatment did not induce DNA fragmentation in either cell line. Correspondingly, treatment of cells with PMA before anti-Fas antibody or A23187 treatment partially inhibited induction of DNA fragmentation in NOS4 cells but not in SKOV-3 cells. Both NOS4 and SKOV-3 cell lines expressed isozymes of PKC at comparable levels. These results suggest the presence of a PKC-dependent anti-apoptotic mechanism in association with high sensitivity to anti-Fas antibody in these ovarian cancer cell lines.

Evaluation of renal function from 99mTc-MAG3 renography without blood sampling

To develop a camera-based method for evaluating renal function with 99mTc-mercaptoacetyltriglycine (MAG3), we examined the relationship between various renogram parameters and 99mTc-MAG3 clearance.

METHODS

Twenty-one patients underwent renal scintigraphy with 99mTc-MAG3. Eighty 3-s frames were obtained after the bolus injection of 250 MBq tracer, followed by the collection of 52 30-s frames. Regions of interest were drawn for the kidneys, perirenal background areas and subrenal background areas, and background-subtracted renograms were generated. Renal accumulation at 0.5-1.5, 0.5-2, 1-2, 1-2.5 and 1.5-2.5 min after tracer arrival in the kidney was calculated as area under the background-subtracted renogram, and percent renal uptake was obtained after correction for soft-tissue attenuation and injected dose. The slope of the renogram was determined for the same segments used in calculating area under the renogram, and slope index was computed as slope corrected for attenuation and injected dose. Percent renal uptakes and slope indices were correlated by linear regression analysis with 99mTc-MAG3 clearance measured using a single blood sampling method.

RESULTS

Among the values of percent renal uptake, the value obtained at 1.5-2.5 min using the perirenal background correlated best with 99mTc-MAG3 clearance. The slope index at 0.5-1.5 or 0.5-2 min using the subrenal background provided better accuracy than percent renal uptake for predicting clearance. There were no substantial differences in the relative function of the right kidney between the methods using percent renal uptake and slope index.

CONCLUSION

99mTc-MAG3 clearance can be assessed with acceptable accuracy by a camera-based method. The method based on the slope of the renogram may replace the one based on the area under the renogram in evaluating renal function from 99mTc-MAG3 renograms.

The sarcoplasmic reticulum Ca2+-ATPase (SERCA2) gene promoter activity is decreased in response to severe left ventricular pressure-overload hypertrophy in rat hearts

The sarcoplasmic reticulum Ca2+-ATPase (SERCA2) pump plays a key role in the contraction-relaxation cycle of the myocardium by controlling the intracellular Ca2+ concentration. SERCA2 protein and mRNA expression levels, as well as, SR Ca2+ uptake function are depressed in hypertrophied and failing myocardium. At this time, the molecular mechanisms regulating SERCA2 gene transcription during hypertrophy and heart failure are not completely understood, especially in vivo. Direct gene transfer into adult cardiac tissue has recently been shown to be a useful technique to study in vivo gene regulation. In this study, SERCA2 promoter-luciferase (Luc) reporter constructs of various lengths were injected into the beating left ventricular apex of adult rats (groups = compensated hypertrophy, heart failure, and controls) and the expression level was analysed. Our SERCA2 promoter analyses revealed three positive regulatory regions between -1810 bp and -1110 bp, -658 bp and -284 bp, and -267 bp and -72 bp and a negative regulatory region between -1110 bp and -658 bp, important for in vivo expression in rat hearts. SERCA2 promoter activity was also assessed in rat hearts with compensated pressure-overload hypertrophy (induced by the DOCA-salt treatment) and heart failure (induced by severe ascending aortic constriction). In the DOCA-salt-induced hypertrophy model, SERCA2 promoter activity was similar to that of sham controls. In contrast, severe constriction of the ascending aorta decreased the expression of the -1810 Luc and -1110 Luc constructs by 92.8% and 64.3%, respectively. This study suggests that only severe pressure-overload hypertrophy produces a significant decrease in SERCA2 promoter activity, and the promoter region extending to -1810 bp is sufficient for the down regulation of SERCA2 gene expression.

Deadtime correction in measurement of fractional renal accumulation of 99Tcm-MAG3

Fractional renal accumulation of a radiotracer is often used to measure renal function with camera-based methods. We evaluated the effect of deadtime count loss on the calculation of fractional renal accumulation of 99Tcm-mercaptoacetyltriglycine (99Tcm-MAG3). In 15 patients, dynamic renal scintigraphy was performed after the injection of 250 MBq of 99Tcm-MAG3. A reference source was placed on the periphery of the field of view of the gamma camera to monitor the loss of counts in dynamic imaging. The activity in the syringe was also counted with the camera to measure the injected dose, and the deadtime count loss in the syringe was computed from the observed count rate and deadtime in imaging a point source. Fractional renal accumulation, the ratio of renal accumulation on dynamic imaging to the injected dose, was assessed with and without correction for deadtime loss. Fractional renal accumulation was over-estimated by 4.1% with no deadtime correction, when the value after correction for loss in both syringe counts and dynamic imaging was used as a standard. It was underestimated by 4.0% with correction for syringe counts only. The results suggest that correction for count loss only in measuring the injected dose does not lead to a significant improvement in the accuracy of estimating renal function with camera-based methods.

Inhibition of complement-mediated immune hemolysis by peptides derived from the constant domain of immunoglobulin

High-dose administration of intravenous immunoglobulin is reported to be useful for inhibiting complement-dependent immune cytolysis. We have found that, among the proposed C1q-binding sites of the Fc portion of human IgG1, only residues 282-292 inhibited pig red blood cell lysis by human serum. Moreover, a hexadecemeric multiple antigen peptide of residues 282-292 from IgG showed significantly greater activity in suppressing complement-mediated immune cytolysis and can be used in place of high-dose intravenous immunoglobulin, which is extracted from donors and thus is expensive.

Metallothionein induction in rat liver by dietary restriction or exercise and reduction of exercise-induced hepatic lipid peroxidation

Metallothioneins (MTs) occur throughout the animal kingdom and they are induced in vivo by metals, hormones, cytotoxic agents, and some kind of stress. It is well known that various stresses such as starvation and immobilization can induce MT synthesis in animal tissues, but the influence of dietary restriction is unknown. The MT levels in the liver increased by food-deprivation and then decreased by refeeding, and a long period of starvation down-alters hepatic MT levels. When the stress is intensified, the induced quantity of hepatic MT is reduced. It became clear that hepatic MT concentrations are controlled within a two fold limit when stressed by dietary restriction. MT was also induced in rat liver at recovery stage following an exhaustive running exercise, and thionein was synthesized first and then zinc bound to the protein. The half-life of hepatic MT induced by exercise (which is a nonmetallic inducer) was estimated at 5.2 h. Preinduced MT markedly suppressed exercise-induced lipid peroxidation in rat liver.

Combination splitting using both in situ and ex situ techniques in triple split liver transplantation in pigs

In situ splitting of cadaver livers has been reported to reduce cold ischemic damage, to avoid biliary complications, and to result in improved graft survival. In this study, which involved a wider application of split liver transplantation (SLT), we examined the effects of a technique combining both ex situ and in situ splittings in triple SLT in pigs and compared it to ex situ splitting alone. In the combination splitting group, the splitting between the right and left lobes was done in situ with perfusion of the left lobe with cold, lactated Ringer's solution; that between the lateral and medical right lobes was done ex situ in backtable surgery. The time required for in situ splitting was 28 +/- 5 min. The time for backtable surgery and the total ischemia time were significantly shorter in the combination splitting group than that in the ex situ splitting group (P < 0.05). One day after triple SLT, the elevations in both serum AST and LDH in the ex situ splitting group were significantly greater than those in the combination splitting group (P < 0.05). We conclude that combination splitting may provide a technical improvement and have a beneficial effect on the clinical application of triple SLT.