Time course and spatial distribution of fMRI signal changes during single-pulse transcranial magnetic stimulation to the primary motor cortex

Simultaneous transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) may advance the understanding of neurophysiological mechanisms of TMS. However, it remains unclear if TMS induces fMRI signal changes consistent with the standard hemodynamic response function (HRF) in both local and remote regions. To address this issue, we delivered single-pulse TMS to the left M1 during simultaneous recoding of electromyography and time-resolved fMRI in 36 healthy participants. First, we examined the time-course of fMRI signals during supra- and subthreshold single-pulse TMS in comparison with those during voluntary right hand movement and electrical stimulation to the right median nerve (MNS). All conditions yielded comparable time-courses of fMRI signals, showing that HRF would generally provide reasonable estimates for TMS-evoked activity in the motor areas. However, a clear undershoot following the signal peak was observed only during subthreshold TMS in the left M1, suggesting a small but meaningful difference between the locally and remotely TMS-evoked activities. Second, we compared the spatial distribution of activity across the conditions. Suprathreshold TMS-evoked activity overlapped not only with voluntary movement-related activity but also partially with MNS-induced activity, yielding overlapped areas of activity around the stimulated M1. The present study has provided the first experimental evidence that motor area activity during suprathreshold TMS likely includes activity for processing of muscle afferents. A method should be developed to control the effects of muscle afferents for fair interpretation of TMS-induced motor area activity during suprathreshold TMS to M1.

Role of 2-deoxy-2-[F-18] fluoro-D-glucose positron emission tomography in the management of bone and soft-tissue metastases

We retrospectively reviewed 71 histopathologically-confirmed bone and soft-tissue metastases of unknown origin at presentation. In order to identify the site of the primary tumour all 71 cases were examined with conventional procedures, including CT, serum tumour markers, a plain radiograph, ultrasound examination and endoscopic examinations, and 24 of the 71 cases underwent 2-deoxy-2-[F-18] fluoro-D-glucose positron emission tomography (FDG-PET). This detected multiple bone metastases in nine patients and the primary site in 12 of the 24 cases; conventional studies revealed 16 primary tumours. There was no significant difference in sensitivity between FDG-PET and conventional studies. The mean maximal standardised uptake value of the metastatic tumours was significantly higher than that of the primary tumours, which is likely to explain why FDG-PET did not provide better results. It was not superior to conventional procedures in the search for the primary site of bone and soft-tissue metastases; however, it seemed to be useful in the staging of malignancy.

Lamin A/C gene mutations in familial cardiomyopathy with advanced atrioventricular block and arrhythmia

Lamin A and C proteins, encoded by the lamin A/C gene (LMNA), are inner nuclear membrane proteins predominantly expressed in terminally differentiated cells. Mutations in LMNA can cause various forms of cardiomyopathy with arrhythmia in an autosomal dominant manner. We collected and evaluated the clinical characteristics of unclassified familial cardiomyopathy with advanced AV block and sporadic cases with advanced AV block. Mutation in LMNA was directly screened using the cycle sequencing method in 5 probands of the familial cardiomyopathy and 60 sporadic cases with advanced AV block. In four of the five familial cases (80%), we identified four distinct mutations: two protein-truncation mutations, R225X and 815_818delinsCCAGAC, and two missense mutations, Y259H and R166P. No sporadic cases carried LMNA mutation. Left ventricular end-diastolic diameter (LVEDD) was slightly enlarged in LMNA mutant carriers (123.5 +/- 9.5%) as well as in non-carriers (125.1 +/- 13.3%), while left ventricular fractional shortening (LVFS) was preserved in LMNA mutant carriers (32.3 +/- 4.8%) and non-carriers (37.6 +/- 6.8%). In LMNA mutation carriers, the average age at onset of advanced AV block is significantly lower than that in non-carriers (43.7 +/- 9.5 vs. 65.3 +/- 13 yr., p < 0.01). Ventricular tachycardia, sudden death, and poor prognosis were observed in LMNA mutation carriers. LMNA mutation could cause familial cardiomyopathy with insignificant LV remodeling, early-age onset of advanced AV block, and lethal ventricular arrhythmia. Screening of LMNA mutation might be beneficial for risk stratification and clinical management of this type of unclassified familial cardiomyopathy.

Cytokine synthesis by chondroblastoma: relation to local inflammation

PURPOSE

To investigate cytokine production by chondroblastoma in inducing local inflammation and adjacent-joint arthritis.

METHODS

Immunohistochemical analyses of curetted tissues using anti-human interleukin (IL)-1 beta, IL- 6, IL-8, and tumour necrosis factor (TNF)-alpha were performed for 6 patients with chondroblastoma and 3 patients with giant cell tumour (GCT) of bone. In addition, prostaglandin E2, IL-1 beta, IL-2, IL-4, IL-5, IL-6, IL-8, and TNF-alpha in the cyst fluid of one of the patients with chondroblastoma and 2 with GCT of bone were measured using immunoassay kits.

RESULTS

More positive staining for IL-1 beta, IL-8, IL- 6, and TNF-alpha was shown in chondroblastoma than GCT of bone samples. Osteoclast-like giant cells in chondroblastomas showed positive staining for IL- 6 only. In addition, concentrations of IL-4, IL-6, and IL-8 in the cyst fluid were higher in the one patient with chondroblastoma than the 2 patients with GCT of bone.

CONCLUSION

Cytokines such as IL-1 beta, IL-8, TNF-alpha, and particularly IL-6 play an important role in local inflammation in patients with chondroblastoma.

Sarcomere mechanics in uniform and nonuniform cardiac muscle: a link between pump function and arrhythmias

Starling's law and the end-systolic pressure-volume relationship (ESPVR) reflect the effect of sarcomere length (SL) on the development of stress (sigma) and shortening by myocytes in the uniform ventricle. We show here that tetanic contractions of rat cardiac trabeculae exhibit a sigma-SL relationship at saturating [Ca2+] that depends on sarcomere geometry in a manner similar to that of skeletal sarcomeres and the existence of opposing forces in cardiac muscle shortened below slack length. The sigma-SL -[Ca2+](free) relationships (sigma-SL-Ca relationships) at submaximal [Ca2+] in intact and skinned trabeculae were similar, although the sensitivity for Ca2+ of intact muscle was higher. We analyzed the mechanisms underlying the sigma-SL-Ca relationship by using a kinetic model assuming that the rates of Tn-C Ca2+ binding and/or cross-bridge (XB) cycling are determined by either the SL, [Ca2+], or sigma. We analyzed the correlation between the model results and steady-state sigma measurements at varied SL at [Ca2+] from skinned rat cardiac trabeculae to test the hypotheses that the dominant feedback mechanism is SL-, sigma-, or [Ca2+]-dependent, and that the feedback mechanism regulates Tn-C Ca2+ affinity, XB kinetics, or the unitary XB force. The analysis strongly suggests that the feedback of the number of strong XBs to cardiac Tn-C Ca2+ affinity is the dominant mechanism regulating XB recruitment. Using this concept in a model of twitch-sigma accurately reproduced the sigma-SL-Ca relationship and the time courses of twitch sigma and the intracellular [Ca2+]i. The foregoing concept has equally important repercussions for the nonuniformly contracting heart, in which arrhythmogenic Ca2+ waves arise from weakened areas in the cardiac muscle. These Ca2+ waves can reversibly be induced with nonuniform excitation-contraction coupling (ECC) by the cycle of stretch and release in the border zone between the damaged and intact regions. Stimulus trains induced propagating Ca2+ waves and reversibly induced arrhythmias. We hypothesize that rapid force loss by the sarcomeres in the border zone during relaxation causes Ca2+ release from Tn-C and initiates Ca2+ waves propagated by the sarcoplasmic reticulum (SR). Modeling of the response of the cardiac twitch to rapid force changes using the feedback concept uniquely predicts the occurrence of [Ca2+]i transients as a result of accelerated Ca2+ dissociation from Tn-C. These results are consistent with the hypothesis that a force feedback to Ca2+ binding by Tn-C is responsible for Starling's law and the ESPVR in the uniform myocardium and leads to a surge of Ca2+ released by the myofilaments during relaxation in the nonuniform myocardium, which initiates arrhythmogenic propagating Ca2+ release by the SR.

Prognostic value of anemia in predicting sudden death of patients with diastolic heart failure

It has been reported that anemia is a prognostic predictor in patients with diastolic heart failure (DHF), however, the relationship between anemia and sudden death in those patients is still unclear. We prospectively studied 357 stable DHF patients and the proportion of anemic patients was 39% of the study population. During the mean follow-up period of 3.6+/-1.7 years, 30 (8.4%) patients died suddenly. Importantly, the Cox proportional-hazards regression analysis showed that lower hemoglobin level was significantly associated with the development of sudden death in the multivariate model (P<0.001). Anemia may be an important therapeutic target to reduce sudden death in DHF patients.

Accumulation of risk markers predicts the incidence of sudden death in patients with chronic heart failure

BACKGROUND

Sudden death is common in chronic heart failure (CHF). Risk stratification is the first step for primary prevention.

AIM

To evaluate the use of risk markers for estimating sudden death risk.

METHODS AND RESULTS

We prospectively examined 680 stable patients with CHF. Risk markers were evaluated using the Cox's proportional hazard model in a stepwise manner. Ejection fraction <30%, left ventricular end-diastolic diameter >60 mm, brain natriuretic peptide >200 pg/ml, non-sustained ventricular tachycardia, and diabetes were significantly associated with increased risk of sudden death. When the number of risk markers were included as co-variables, only "number of risk markers >or=3'' entered the model (hazard ratio 8.95, 95% confidence interval 4.57-17.52), while the effects of individual markers did not enter the model. The annual mortality from sudden death was 11% in patients with 3 or more risk markers and 1.4% in patients with 2 or less.

CONCLUSIONS

Rather than particular risk markers, the number of accumulated risk markers was a more powerful predictor for sudden death in patients with CHF. The number of risk markers could be useful for risk stratification of sudden death.

Monophasic action potential duration at the crista terminalis in patients with sinus node disease

BACKGROUND

The repolarization properties of the crista terminalis (CT) cells have not been elucidated in patients with sinus node disease (SND). In the present study a new technique of recording the monophasic action potential (MAP) at the CT was used to examine the repolarization of the right atrium (RA) in SND patients.

METHODS AND RESULTS

Symptomatic SND (n=13) patients and age-, sex-matched control patients (n=13) were tested. The MAP duration (MAPD) at a basic cycle length of 600 ms was recorded at the CT in the superior vena cava - RA junction and at the middle - anterior RA with the effective refractory period (ERP) at the high RA. In 6 controls and 4 SND patients, the effect of adenosine triphosphate on the MAPD was examined. The MAPD at the CT exceeded that at the middle - anterior RA in both groups. The MAPD at the CT in the SND group was significantly prolonged compared with the control group (CT: 358+/-39 ms vs 289+/-43 ms). Between the SND and control groups, the MAPD at the middle - anterior RA (278+/-36 ms vs 265+/-39 ms) and ERP (294+/-42 ms vs 266+/-41 ms) did not differ. Both the corrected-sinus node recovery time and sinoatrial conduction time were better correlated with the MAPD at the CT than the MAPD at the middle - anterior RA and ERP. Adenosine triphosphate shortened the MAPD, which was augmented at the CT in the SND patients.

CONCLUSION

A novel method of estimating the MAP at the CT revealed the characteristics of atrial repolarization in SND patients.

Arrhythmogenic Ca2+ release from cardiac myofilaments

We investigated the initiation of Ca(2+)waves underlying triggered propagated contractions (TPCs) occurring in rat cardiac trabeculae under conditions that simulate the functional non-uniformity caused by mechanical or ischemic local damage of the myocardium. A mechanical discontinuity along the trabeculae was created by exposing the preparation to a small constant flow jet of solution with a composition that reduces excitation-contraction coupling in myocytes within that segment. Force was measured and sarcomere length as well as [Ca(2+)](i) were measured regionally. When the jet-contained Caffeine, BDM or Low-[Ca(2+)], muscle-twitch force decreased and the sarcomeres in the exposed segment were stretched by shortening of the normal regions outside the jet. During relaxation the sarcomeres in the exposed segment shortened rapidly. Short trains of stimulation at 2.5 Hz reproducibly caused Ca(2+)-waves to rise from the borders exposed to the jet. Ca(2+)-waves started during force relaxation of the last stimulated twitch and propagated into segments both inside and outside of the jet. Arrhythmias, in the form of non-driven rhythmic activity, were triggered when the amplitude of the Ca(2+)-wave increased by raising [Ca(2+)](o). The arrhythmias disappeared when the muscle uniformity was restored by turning the jet off. We have used the four state model of the cardiac cross bridge (Xb) with feedback of force development to Ca(2+) binding by Troponin-C (TnC) and observed that the force-Ca(2+) relationship as well as the force-sarcomere length relationship and the time course of the force and Ca(2+) transients in cardiac muscle can be reproduced faithfully by a single effect of force on deformation of the TnC.Ca complex and thereby on the dissociation rate of Ca(2+). Importantly, this feedback predicts that rapid decline of force in the activated sarcomere causes release of Ca(2+) from TnC.Ca(2+),which is sufficient to initiate arrhythmogenic Ca(2+) release from the sarcoplasmic reticulum. These results show that non-uniform contraction can cause Ca(2+)-waves underlying TPCs, and suggest that Ca(2+) dissociated from myofilaments plays an important role in the initiation of arrhythmogenic Ca(2+)-waves.

Changes in biochemical parameters after anterior cruciate ligament injury

We studied the biochemical characteristics of human knees with deficient anterior cruciate ligaments (ACL) and analysed their relationship to the time after ligamentous injury. Thirty-two patients with isolated ACL-injured knees and six healthy volunteers were enrolled. Synovial fluid samples were centrifuged after aspiration during arthroscopic examination, and aliquots of supernatant were frozen and stored at -80 degrees C. The samples were analysed for interleukin (IL)-1beta, tumour necrosis factor (TNF)-alpha, IL-6, matrix metalloproteinase (MMP)-3, and tissue inhibitor of metalloproteinase (TIMP)-1 using commercially available sandwich enzyme-linked immunosorbent assay. In fluid from ACL-injured knees, the average concentrations of IL-6, MMP-3 and TIMP-1 were highly elevated in comparison with normal controls. There was a statistically significant correlation between the concentrations of MMP-3 and IL-6. The IL-6 and TIMP-1 concentrations were interrelated. The concentration of MMP-3 remained high, independent of the duration since the injury, whereas the TIMP-1 and IL-6 levels decreased. The results suggest that the timing of the treatment of an ACL-injured knee might be of importance.

Osteoid osteoma treated with computed tomography-guided percutaneous radiofrequency ablation: a case series

The nidi of osteoid osteoma are small and difficult to identify precisely; this can necessitate substantial resection of the surrounding normal bone. We applied percutaneous, image-guided radiofrequency ablation to treat 5 patients with osteoid osteoma. The precise location of each nidus was determined using a 3-mm-thick spiral computed tomographic scan. The most appropriate needle pathway was selected to avoid major neural and vascular structures. A 14-gauge core needle was introduced into the nidus and then exchanged for a 17-gauge straight rigid electrode with a 1-cm exposed tip to heat the lesion to 90 degrees centigrade for 5 minutes. Four of the 5 patients were discharged on the day after surgery without any external supports, and were pain-free after a few days. The remaining patient had a pes equinus contracture induced by the penetration of the calf muscles through a posterior approach but was fully recovered 6 days later. The mean follow-up period was 20.6 months. No recurrences or late complications were observed in this series. This case series shows that the computed tomography-guided percutaneous radiofrequency ablation is a simple, minimally invasive, and highly effective technique for the treatment of osteoid osteoma.