Synergistic effects of MAP2 and MAP1B knockout in neuronal migration, dendritic outgrowth, and microtubule organization

MAP1B and MAP2 are major members of neuronal microtubule-associated proteins (MAPs). To gain insights into the function of MAP2 in vivo, we generated MAP2-deficient (map2(-/-)) mice. They developed without any apparent abnormalities, which indicates that MAP2 is dispensable in mouse survival. Because previous reports suggest a functional redundancy among MAPs, we next generated mice lacking both MAP2 and MAP1B to test their possible synergistic functions in vivo. Map2(-/-)map1b(-/-) mice died in their perinatal period. They showed not only fiber tract malformations but also disrupted cortical patterning caused by retarded neuronal migration. In spite of this, their cortical layer maintained an "inside-out" pattern. Detailed observation of primary cultures of hippocampal neurons from map2(-/-)map1b(-/-) mice revealed inhibited microtubule bundling and neurite elongation. In these neurons, synergistic effects caused by the loss of MAP2 and MAP1B were more apparent in dendrites than in axons. The spacing of microtubules was reduced significantly in map2(-/-)map1b(-/-) mice in vitro and in vivo. These results suggest that MAP2 and MAP1B have overlapping functions in neuronal migration and neurite outgrowth by organizing microtubules in developing neurons both for axonal and dendritic morphogenesis but more dominantly for dendritic morphogenesis.

Quantification of limited augmentation of myocardial (99m)Tc-tetrofosmin uptake at exercise in stable coronary artery disease

We evaluated the diagnostic accuracy of a new method for quantitative analysis of myocardial perfusion at exercise using (99m)Tc-tetrofosmin tomographic imaging. (99m)Tc-tetrofosmin imaging of an exercise-rest sequence was performed in 30 patients with coronary artery disease (CAD) and eight age-matched control subjects. The exercise-induced myocardial count increase was calculated as the relative value (per cent increase ratio, %IR) to that at rest by correcting for physical decay for (99m)Tc and injected doses and by a subtraction technique. Exercise and rest (99m)Tc-tetrofosmin images were assessed visually and quantitatively using the per cent peak count and %IR of the myocardial count at exercise. Segments with significant coronary stenosis (diameter stenosis=75% or more) showed a significantly lower %IR than did those without significant coronary stenosis in the CAD patients (37+/-19% vs 63+/-21%, P<0.05). The diagnostic efficacy of visual analysis for detecting coronary stenosis was as follows: sensitivity, 58.1% and specificity, 81.4%. When %IR=37% was used for detecting significant coronary stenosis, sensitivity and specificity increased to 74.2% and 93.2%, respectively. Furthermore, the quantitative analysis significantly (P=0.04) improved the overall diagnostic accuracy from 73.3% to 86.7% compared to that of visual assessment. Thus, augmentation of myocardial (99m)Tc-tetrofosmin uptake at exercise is blunted in the myocardium with significant coronary stenosis. The calculation of myocardial count increase at exercise relative to that at rest can improve the diagnostic value of (99m)Tc-tetrofosmin SPECT imaging and may contribute to more accurate quantification of myocardial ischaemia and impaired tracer uptake in coronary artery disease.

[Blood transfusion under cardiopulmonary bypass is a possible inducer for inflammation?]

To investigate that blood transfusion under cardiopulmonary bypass is a possible inducer for inflammation, a retrospective study was made with 20 adult patients who underwent coronary artery bypass grafting. The subjects were divided into two groups; transfusion group (group T) including 9 patients who received blood transfusion during cardiopulmonary bypass and the control group (group C) including 11 patients who did not undergo perioperative transfusion. Respiratory index as an indicator of respiratory functions was determined before and immediately after cardiopulmonary bypass, at the end of surgery and 4 hours thereafter. Cardiac index and arterial pressure were determined as the indicator of cardiac function. Moreover, interleukin 6 and 8 (IL-6 and IL-8), inflammatory cytokines were measured and compared between the two groups. The mean amount of blood transfusion was 2.1 units per individual of group T. The minimum value of hematocrit during cardiopulmonary bypass was significantly lower in group T (15.8 +/- 1.8%) than group C (19.1 +/- 1.4%), but the difference became not significant after cardiopulmonary bypass. There were no significant differences either in aortic pressure or cardiac index between two groups. The respiratory index at the end of surgery was higher in group T but the difference was not significant. Meanwhile IL-8 level at the end of cardiopulmonary bypass was significantly higher in group T (67.9 +/- 36 pg/ml) than group C (35.1 +/- 21 pg/ml). However, there was no difference in IL-6 level between the two. These results suggested that inflammation might be aggravated by an increase of IL-8 induced by blood transfusion.

Unusual coronary artery aneurysm and acute myocardial infarction in a middle-aged man with systemic lupus erythematosus

A 55-year-old man developed acute myocardial infarction (AMI) related to a large coronary artery aneurysm and a distal coronary stenotic lesion after steroid therapy for systemic lupus erythematosus (SLE). Only 13 SLE patients with AMI caused by coronary artery aneurysms have been reported, 11 of whom were young or middle-aged women and the 2 remaining were young men. This is the first report of a middle-aged man with multiple coronary lesions.

Representation of molecular configurations by CAST coding method

A configurational CAST (CAnonical representation of STereochemistry) coding method, which represents relative and absolute configuration, is described. The configurational CAST codes are constructed by canonical rotation of the dihedral angles of the input structure before the CAST codes are assigned. Using the configurational CAST, configurational differences can be distinguished independently of conformational differences. Representation of enantiomers is also achieved by a mirror image conversion method. The CAST representation shows the distinctive characteristics of several diastereomers and conformers that were examined. The method clearly represents the differences in configurations. Applications to organic molecules having complex stereochemistry are also demonstrated.

Stereoselective syntheses of the C'D'E'F'-ring system of maitotoxin and the FG-ring system of gambierol

[structure: see text]. The stereoselective syntheses of the C'D'E'F'-ring system of maitotoxin and the FG-ring system of gambierol were accomplished. The key steps involve 6-endo-cyclization of methylepoxide, SmI2-induced reductive cyclization, 6-endo-cyclization of vinylepoxide, and formation of the lactone ring.

Cytoplasmic gamma actin as a Z-disc protein

To investigate the precise localization of cytoplasmic gamma actin in skeletal muscle and the relationship to dystrophin molecules, we designed an antibody against the N-terminal peptide of cytoplasmic gamma actin. Western blot analysis using SDS-PAGE and isoelectric focusing (IEF) gel revealed that the antibody reacted only with the actin isoforms having gamma motility, confirming that the antibody is specific to the cytoplasmic (nonmuscle) gamma actin. Immunohistochemical analysis of the skeletal muscle of the adult mouse revealed a dot-like staining pattern of the antibody in transverse sections and a striated staining pattern in longitudinal sections. The double immunostaining technique revealed the colocalization of cytoplasmic gamma actin with alpha-actinin, implying the localization of the actin on the Z-disc. Contrary to previous findings (1), we did not detect the colocalization of cytochrome oxidase, a mitochondria marker, with this actin.

Crow-Fukase syndrome with ischemic cardiomyopathy

A 31-year-old man was admitted to our hospital for further evaluation of heart failure symptoms. Crow-Fukase syndrome was diagnosed on the basis of findings of polyneuropathy, hepatomegaly, monoclonal hypergammaglobulinemia, and hypertrichosis. Dipyridamole-stress thallium-201 perfusion imaging, contrast left ventriculography, and coronary angiography revealed a markedly dilated and dysfunctioning left ventricle, extensive reversible ischemia with fixed defect, and multiple coronary lesions. Histopathology of myocardial biopsy specimens demonstrated ischemia-induced myocardial necrosis. These findings suggested that ischemic cardiomyopathy, probably due to inflammatory reactions of coronary arteries in Crow-Fukase syndrome, was responsible for the heart failure symptoms and left ventricular dysfunction in this patient.

[Evaluation of a combination chemotherapy with nedaplatin and 5-FU for oral cancers]

Nedaplatin (cis-diammine-glycolato platinum: CDGP) is a platinum compound with a molecular weight of 303.18 that was recently developed in Japan. There have been reports of the antineoplastic effects of Nedaplatin on cancers in the cranio-cervical region, lung, esophagus, urinary bladder, testis, ovary, and uterus. In this study, we performed combined therapy of CDGP and fluorouracil (5-FU) for 8 patients with oral cancers, and evaluated the results to elucidate the clinical effect and adverse side effects. The subjects were 8 patients with squamous cell carcinoma (5 males and 3 females aged 33-65 years). The primary carcinoma regions were the tongue in 5 patients, oral floor in 2 patients, and mandibular gingiva in 1 patient. The T-classification was T2 in 6 patients and T4 in 2 patients, and the clinical staging was Stage II in 5 patients, Stage III in 1 patient and Stage IV in 2 patients. We first administered 700 mg/m2 5-FU per day from day 1 to day 5 (total dose 3,500 mg/m2), then 90 mg/m2 CDGP on day 5. The clinical effect was evaluated as a partial response in all cases, showing a 100% success rate. The histopathological findings of resected tumors were evaluated by Ohboshi and Shimozato's classification. One patient was Grade IIA, 5 patients Grade IIB, and 2 patients Grade III. The adverse side effects were slight myelotoxicity, gagging, nausea, alopecia, and stomatitis less than Grade II. Although the oral cancers in this study were extroverted superficial ulcerative cancers, and the number of patients was low at 8, this combined therapy is considered useful and worth evaluating in further accumulated cases.

[Clinical application of gated SPECT imaging to regional function assessment: current status and limitations]

It is likely that clinical applications of ECG-gated single-photon emission computed tomography (SPECT) are established in nuclear cardiology practice because of the improved diagnostic accuracy of gated SPECT imaging for the detection of coronary artery disease and because this technique enables not only simultaneous assessment of myocardial perfusion and function but also improvement of risk stratification of coronary patients. Although a gated approach with SPECT imaging has been demonstrated to have high reproducibility and reliability for quantifying global function, there are several limitations in appropriate processing of 4-dimensional data for quantitative assessment of regional function. Even if limited spatial and temporal resolutions and a lack of attenuation and scatter corrections are disregarded, sufficient data collection, image-quality control, and precise application of algorithms to gated SPECT data are prerequisite. The results of several kinds of quantitative analysis of regional cardiac function, such as regional wall motion (distance deviation of the inner myocardial border), regional ejection fraction, percent wall thickening, and percent count increase with or without self-normalization have been reported. Further clinical application of quantitative regional function assessment by a gated SPECT technique, however, requires standardization of data acquisition, data analysis, and data presentation with appropriate quantitative parameters; production of a standard map using quantitative values; and validation study by comparison with results of visual analysis and other modalities in a large-scale patient population.

Charcot-Marie-Tooth disease type 2A caused by mutation in a microtubule motor KIF1Bbeta

The kinesin superfamily motor protein KIF1B has been shown to transport mitochondria. Here, we describe an isoform of KIF1B, KIF1Bbeta, that is distinct from KIF1B in its cargo binding domain. KIF1B knockout mice die at birth from apnea due to nervous system defects. Death of knockout neurons in culture can be rescued by expression of the beta isoform. The KIF1B heterozygotes have a defect in transporting synaptic vesicle precursors and suffer from progressive muscle weakness similar to human neuropathies. Charcot-Marie-Tooth disease type 2A was previously mapped to an interval containing KIF1B. We show that CMT2A patients contain a loss-of-function mutation in the motor domain of the KIF1B gene. This is clear indication that defects in axonal transport due to a mutated motor protein can underlie human peripheral neuropathy.

Studies on the prevalence of complicated atrial arrhythmias, flutter, and fibrillation in patients with reciprocating supraventricular tachycardia before and after successful catheter ablation

Atrial flutter and AF are complications in approximately 30% of cases of paroxysmal supraventricular tachycardia (PSVT)-indicated catheter ablation, and it is of interest to determine if therapeutic modification for PSVT would eliminate combined atrial tachyarrhythmia like atrial flutter and AF. The aim of this study was to determine the incidence and the risk of atrial tachyarrhythmias after catheter ablation of PSVT. A total of 152 patients (age range 12-74, mean 41 +/- 17 years) with accessory pathway (n = 106) and/or dual atrioventricular nodal conduction (n = 46) were enrolled in a 2-year follow-up program after successful catheter ablation. Possible risks on clinical background (age, sex, PSVT duration, hemodynamic instability during attacks), premature atrial contraction (PACs) on Holter monitoring, echocardiographic left atrial size, and electrophysiological property (insertion site, conduction type, effective refractory period) were evaluated. Atrial flutter and AF were complications in 53 (35%) of the subjects, who were elderly and had a longer PSVT history with a larger left atrial dimension and frequent PACs; however, the electrophysiological properties were similar. After a 2-year follow-up period 36 (24%) of the patients still exhibited PAC runs, including 13 (9%) with atrial flutter and AF, each one of whom were complicated with nonlethal cerebral thromboembolism and congestive heart failure. Multiplelogistic-regression analysis revealed that advanced age (> or = 41 years, P = 0.0152) and frequent PACs (> or = 1% of total daily QRS counts, P = 0.0426) on Holter monitoring are the risk factors of PAC runs and/or atrial flutter and AF. In conclusion, successful ablation for PSVT is thought to be beneficial for preventing atrial flutter and AF. However, careful follow-up to monitor for the recurrence and atrial flutter and AF related complications, especially in patients of solitary atrial flutter and AF without reciprocating tachycardia and with frequent PAC.

Technetium-99m sestamibi/tetrofosmin myocardial perfusion scanning in cardiac and noncardiac sarcoidosis

Left ventricular (LV) and right ventricular (RV) involvement in sarcoidosis must be firmly confirmed to determine patients' prognosis. We examined whether myocardial perfusion images using technetium-99m single photon emission computed tomography (SPECT) have a diagnostic benefit in the evaluation of biventricular involvement. Sixteen patients with sarcoidosis, aged 21-78 (54 +/- 12) years old, 5 males and 11 females, complicated with cardiac disease (cardiac sarcoidosis, n = 6) including tachyarrhythmias of ventricular origin (n = 5), atrioventricular block (n = 4), and congestive heart failure (NYHA > or = II, n = 1), were enrolled in this study. Myocardial SPECT using technetium-99m sestamibi or tetrofosmin was performed and semiquantitatively scored for comparison with 25 control subjects. Perfusion abnormalities were more frequently recognized in sarcoidosis (LV 5/16, 31% and RV 14/16, 88% vs. LV 0/25, 0% and RV 8/25, 32% in controls). LV involvement had a close correlation with atrioventricular block and with congestive heart failure, and multiple sites of RV involvement correlated with ventricular tachyarrhythmia of RV origin. Total number of defect segments were highest in cardiac sarcoidosis (18/30, 60% vs. 19/60, 32% in noncardiac sarcoidosis, and 11/150, 7% in controls, p = 0.0001), and semiquantitatively evaluated total LV and RV scores (ranging from 0 to 18) were higher than those of controls (15.1 +/- 1.8 vs. 11.4 +/- 3.0 in noncardiac sarcoidosis, and 9.0 +/- 5.0 in cardiac sarcoidosis) and exhibited a significant positive linear correlation with the RV ejection fraction (y = 19.8 + 1.83x, r = 0.786, p = 0.001). Biventricular SPECT using technetium-99m is clinically useful for the noninvasive evaluation of both ventricular involvements in sarcoidosis.

Effects of a phosphodiesterase III inhibitor on circulating blood volume after cardiopulmonary bypass

Using a new method based on pulse dye densitometry, circulating blood volume (BV) was measured without direct sampling in patients undergoing open-heart surgery, and the effects of phosphodiesterase (PDE) III inhibitor administration during cardiopulmonary bypass (CPB) were evaluated. Sixteen patients scheduled for elective coronary artery bypass grafting were randomly assigned to the PDE III inhibitor group or control group. BV was determined before CPB, and immediately, and 4 and 12h after operation. After declamping of the aorta, the PDE III inhibitor amrinone (1 mg/kg) was infused as a single bolus into the venous reservoir in the PDE III inhibitor group. BV decreased significantly soon after the operation in the control group. It did not decrease in the PDE III inhibitor group (48.6 +/- 44 and 60.6 +/- 8.0 ml/kg for the control and PDE III inhibitor groups. respectively). Four hours after surgery and beyond no significant changes in BV were observed in either group. The body fluid balance was negative in both groups. In conclusion, a single administration of PDE III inhibitor during CPB was found to sustain BV soon after operation and, therefore, is useful for postoperative management of open-heart surgery.

Defect in human myocardial long-chain fatty acid uptake is caused by FAT/CD36 mutations

Because of the importance of long-chain fatty acids (LCFAs) as a myocardial energy substrate, myocardial LCFA metabolism has been of particular interest for the understanding of cardiac pathophysiology. Recently, by using radiolabeled LCFA analogues, myocardial LCFA metabolism has been clinically evaluated, which revealed a total defect of myocardial LCFA accumulation in a small number of subjects. The mechanism for the cellular LCFA uptake process is still disputable, but recent results suggest that fatty acid translocase (FAT)/CD36 is a transporter in the heart. In the present study, we analyzed mutations and protein expression of the FAT/CD36 gene in 47 patients who showed total lack of the accumulation of a radiolabeled LCFA analogue in the heart. All the patients carried two mutations in the FAT/CD36 gene, and expression of the FAT/CD36 protein was not detected on either platelet or monocyte membranes. Our results showed the link between mutations of the FAT/CD36 gene and a defect in the accumulation of LCFAs in the human heart.

Effect of coronary artery bypass grafting on native coronary artery stenosis. Comparison of internal thoracic artery and saphenous vein grafts

BACKGROUND

The purpose of this study was to investigate the influence of coronary artery bypass grafting on the degree of stenosis of the native coronary artery.

METHODS

EXPERIMENTAL DESIGN

retrospective data analysis.

SETTING

University hospital.

PATIENTS

consecutive patients undergoing coronary artery bypass grafting (n=52). Bypasses using internal thoracic artery grafts (n=26) and saphenous vein grafts (n=37) to incompletely occluded coronary arteries were studied.

INTERVENTIONS

coronary artery bypass grafting using internal thoracic artery or saphenous vein grafts.

MEASURES

stenosis of the native coronary artery on angiography.

RESULTS

Three recipient coronary arteries bypassed with internal thoracic artery grafts (12%) and 14 recipient coronary arteries bypassed with saphenous vein grafts (38%) showed progression of narrowing (p=0.024). Two recipient coronary arteries bypassed with internal thoracic artery grafts (8%) and 13 recipient coronary arteries bypassed with saphenous vein grafts (35%) showed total occlusion (p=0.016). Hypertension, hyperlipidemia, diabetes mellitus, and smoking history did not correlate with progression of stenosis of the native coronary arteries. Graft flow measured during surgery in the saphenous vein grafts was not significantly different between the group that exhibited progression of the native stenosis and the group that did not.

CONCLUSIONS

Coronary artery bypass grafting with saphenous vein grafts may result in progression of stenosis of the recipient coronary artery. This is less likely after coronary artery bypass grafting with internal thoracic artery grafts. This difference may be due to the ability of the pedicled internal thoracic artery graft to regulate flow. Thus competitive flow in the native coronary artery is minimized. This has significant clinical implications.

[Usefulness of right ventricular Doppler index for predicting outcome in patients with dilated cardiomyopathy]

OBJECTIVES

Left ventricular Doppler index (LVDI) is believed to be a useful echocardiographic index of systolic and diastolic ventricular function. However, the usefulness of right ventricular Doppler index (RVDI) remains uncertain, especially in dilated cardiomyopathy. The predictive value of RVDI for estimating long-term cardiac events, including cardiac death, was investigated.

METHODS

Fifty-nine consecutive patients with dilated cardiomyopathy (41 males and 18 females, mean age 52 +/- 15 years) were enrolled in this follow-up study. RVDI and LVDI were calculated as follows: DI = (isovolumic contraction time + isovolumic relaxation time)/ejection time.

RESULTS

During a follow-up period of 3.7 +/- 3.0 years, 27 (46%) of the patients exhibited cardiac events, including cardiac death (n = 9), heart failure (n = 16) and tachyarrhythmias (n = 2) requiring in-hospital treatment. Patients with these cardiac events had higher LVDI and RVDI at the initial follow-up examination, and RVDI had a significant linear correlation with LVDI (LVDI = 0.550 + 0.452 x RVDI, r = 0.530, p = 0.0001). The 6-year survival rate was significantly lower in patients with both LVDI > or = 0.78 and RVDI > or = 0.49 than in other patients (50% vs 75%, respectively, p = 0.009). Cox proportional hazards model analysis showed that RVDI > or = 0.49 was the independent predictor of cardiac events (p = 0.0153) and cardiac death (p = 0.0003).

CONCLUSIONS

RVDI is clinically useful for estimating the outcome of patients with dilated cardiomyopathy.

Cardiac surgery in patients with end-stage renal disease. Utility of continuous ambulatory peritoneal dialysis

OBJECTIVES

The number of patients with end-stage renal disease undergoing open heart surgery continues to grow. We evaluated continuous ambulatory peritoneal dialysis and the extracorporeal ultrafiltration method during cardiopulmonary bypass in the management of these difficult patients.

METHODS

These 2 methods were used in 4 patients with renal failure who underwent open heart surgery between July 1997 and March 1999. Preoperative continuous ambulatory peritoneal dialysis was conducted using standard protocols. Extracorporeal ultrafiltration method was used only during cardiopulmonary bypass. Continuous ambulatory peritoneal dialysis was initiated upon arrival at the intensive care unit. Mean follow-up was 12 months.

RESULTS

Postoperative blood urea nitrogen and creatinine concentrations were lower than preoperative concentrations. No patients required hemodialysis. All 4 patients were discharged to their homes. No deaths occurred.

CONCLUSIONS

Continuous ambulatory peritoneal dialysis and extracorporeal ultrafiltration method are combined to treat patients with end-stage renal disease who require open heart surgery. This combination is simple, and does not require specialized personnel, and obviates the hemodynamic instability associated with hemodialysis.

CD2- CD4+ CD56+ hematodermic/hematolymphoid malignancy

BACKGROUND

CD2- CD4+ CD56+ lymphoid malignancy has been only rarely reported the last 5 years. It is characterized by a high incidence of cutaneous involvement, cytologically agranular cells, aggressive clinical course, and negative Epstein-Barr virus (EBV) involvement.

OBSERVATION

We describe a Japanese patient with a unique hematolymphoid malignancy characterized by an involvement of skin, nasopharyngeal region, bone marrow, lymph node, and a CD4+ CD43+ CD56+ CD2- CD3- CD8- and terminal deoxynucleotidyl transferase phenotype. Clinically, the cutaneous eruptions were purplish, hard, multiple nodules. Histologically, a massive proliferation of atypical pleomorphic cells with medium-sized nuclei were observed throughout the dermis. No clonal rearrangement of T-cell receptor (TCR)-beta gene or immunoglobulin heavy chain J gene was found, and no positive identification of EBV by in situ hybridization for EBV-encoded small nuclear RNA was found. The patient underwent high-dose chemotherapy with autografting of peripheral blood stem cells; however, the tumors quickly relapsed.

CONCLUSION

We gathered data from 17 cases of lymphoid malignancy from the literature sharing immunophenotypic and genotypic features similar to those of our case, including CD2- CD4+ CD56+ and germline rearrangement of TCR. Although the cellular origin could not be decided, this malignancy was found to have 100% affinity for skin, a short course, and poor prognosis.

Role of the central nervous system in the development of hypertension produced by chronic nitric oxide blockade in rats

We examined the role of the central nervous system, and particularly the renin-angiotensin (RA) system, in the development of hypertension produced by chronic inhibition of NO synthesis. In experiment 1, Wistar rats drank either nitro-L-arginine-methyl ester (L-NAME) or tap water. Before L-NAME treatment rats were divided into 6 groups. Four of them were administered either losartan or artificial cerebroventricular fluid (a-CSF) intracerebroventricularly (i.c.v.) for 1 week using an osmotic mini pump. The other two groups were administered the same amount of losartan intravenously (i.v.). In experiment 2, cardiovascular responses to acute i.c.v. losartan and muscimol, a GABA(A) agonist, were examined in conscious L-NAME-treated rats. Finally, in experiment 3, effects of ablation of the AV3V (anteroventral third ventricle) area, known to be one of the centers of cardiovascular control, were tested in the development of L-NAME hypertension. The development of hypertension by L-NAME treatment was attenuated with chronic i.c.v. losartan in a dose-dependent manner, while i.v. losartan had no effect. One week after cessation of i.c.v. losartan, blood pressure was elevated to the same level as in a-CSF-infused, L-NAME-treated rats. Acute i.c.v. losartan produced no cardiovascular changes in either L-NAME-treated or control rats. On the other hand, although i.c.v. muscimol elicited depressor effects in both groups, these responses were significantly larger in L-NAME-treated rats. Cardiovascular responses to i.v. hexamethonium were similar in both groups. The existence of prior lesions in the AV3V area significantly attenuated the development of L-NAME-induced hypertension. These results indicate that the central RA system plays an important role in the development of hypertension produced by chronic inhibition of NO synthase. Moreover, disorder of the central GABA system, rather than that of the RA system, might be important in the maintenance of hypertension in this model.

Impaired exercise-related myocardial uptake of technetium-99m-tetrofosmin in relation to coronary narrowing and diabetic state: assessment with quantitative single photon emission computed tomography

Despite the diagnostic efficacy of stress myocardial perfusion imaging, the correlation between the actual perfusion tracer activity and diseased state of a coronary artery has not been studied in detail. We estimated exercise-related perfusion augmentation in relation to disease states of a coronary artery in diabetic and non-diabetic patients by a newly developed quantitative technetium (Tc)-99m-tetrofosmin myocardial imaging technique. Tc-99m-tetrofosmin tomographic imaging with an exercise-rest protocol was performed in 26 stable coronary patients and in 8 age-matched controls. Percent increase (%IR) in myocardial count during symptom-limited submaximal exercise-stress was calculated in 16 non-infarcted polar map segments and in each coronary territory by a subtraction technique with corrections for physical decay and injected tracer doses, and the results were compared with those of angiographically quantified coronary diameter stenosis (%DS). Percent IR and peak heart rate during exercise showed a positive linear correlation both in coronary territories with significant stenosis (%DS > or = 75%) and in control or nonstenotic (%DS < 75%) territories. The regression line in stenotic regions was, however. significantly (p < 0.01) shifted downward compared to that in non-stenotic regions. Percent IR in stenotic regions showed a significant inverse correlation with %DS. Coronary stenosis of 75% or more was identified by a %IR cutoff value of 40% with 77% sensitivity, 70% specificity, and an accuracy of 72%. In coronary territories with a %DS of less than 75%, %IR in diabetic patients was significantly lower (46+/-15%) than that in nondiabetic patients (61+/-25%). Thus, blunted exercise-related augmentation of myocardial uptake of Tc-99m-tetrofosmin correlates with the severity of coronary narrowing and diabetic state.

Right ventricular abnormalities assessed by myocardial single-photon emission computed tomography using technetium-99m sestamibi/tetrofosmin in right ventricle-originated ventricular tachyarrhythmias

OBJECTIVES

We sought to determine whether right ventricular (RV) perfusion imaging with technetium-99m (Tc-99m) sestamibi or tetrofosmin single-photon emission computed tomography has diagnostic benefit for RV-originated ventricular tachyarrhythmias (RVT).

BACKGROUND

Identification of RV abnormalities is clinically important to establish RVT etiology.

METHODS

Forty-seven patients with RVT (23 with idiopathic and 24 with organic RVT due to arrhythmogenic RV or dilated cardiomyopathy, cardiac sarcoidosis or myocarditis) were compared to 25 control subjects. Right ventricular uptake score, as assessed by modified tomographic imaging, and regional RV count relative to peak left ventricular (LV) count (RV/LV count ratio) were compared with RV regional and global function.

RESULTS

Regional RV uptake score correlated well with the RV/LV count ratio, and segmental abnormality was more frequently (p = 0.001) detected in the organic RVT group (22 [92%] of 24 patients) than in the idiopathic RVT group (4 [17%] of 23 patients) or the control group (8 [32%] of 25 patients). The total RV score (8.4+/-3.8) in the organic RVT group was significantly lower than that in the idiopathic RVT group (15.6+/-1.6) or the control group (15.1+/-1.8). The total RV score correlated with RV EF (r = 0.702, p<0.001). A total RV score <12 differentiated the organic RVT group from the other two groups, with a sensitivity of 79% and a specificity of 100%. The asynergic RV regions had a significantly lower RV/LV count ratio and RV score as compared with the nonasynergic regions and were identified by RV assessment, with a sensitivity of 76.1% and a specificity of 76.6%.

CONCLUSIONS

Right ventricular perfusion tomography using a Tc-99m-labeled tracer is clinically useful for the noninvasive detection of RV myocardial damage in patients with RVT and for differentiating organic from idiopathic RVT.