Nicotine Increases Spatiotemporal Complexity of Ventricular Fibrillation Wavefront on the Epicardial Border Zone of Healed Canine Infarcts

BACKGROUND: The influence of a pharmacologic agent on wavefront dynamics during ventricular fibrillation (VF) in a setting of remodeled and healed myocardial infarction (MI) remains poor explored. We hypothesized that nicotine, by virtue of its complex direct and indirect cardiovascular effects, increases wavefront complexity during VF. Specifically, we sought to determine whether nicotine increases the number and complexity (approximate entropy) of wavelets during stage II VF in hearts with healed MI. METHODS AND RESULTS: The left anterior descending coronary artery was permanently occluded in five mongrel dogs and wavefront dynamics during VF studied 5 to 6 weeks after occlusion in the open-chest anesthetized state. VF was induced by rapid pacing and the activation pattern mapped on the surviving epicardial border zone (EBZ) of the left ventricle with a plaque (3.2 x 3.8 cm) having 477 bipolar electrodes 1.6 mm apart. VF was mapped before and 20 minutes after 5 μg/kg/min nicotine infusion. Nicotine with a mean arterial plasma concentration of 127 +/- 76 ng/mL (range 57 to 240 ng/mL) significantly (P <.01) increased the number of wavelents from 3.8 +/- 0.4 to 5 +/- 0.41. The increased number of wavelets was caused by an increase (P <.01) in the spontaneous breakup of wavefronts from 4.1 +/- 0.9 times/s to 6.9 +/- 1.1 times/s. Wavebreak over the EBZ was functional in nature as no breakup occurred during normal sinus rhythm. Approximate entropy, a measure of complexity, significantly (P <.01) increased after nicotine administration from 0.23 +/- 0.02 to 0.28 +/- 0.01. CONCLUSIONS: Nicotine increases the number of wavelets and their complexity during VF by promoting spontaneous wavebreak over the EBZ of healed MI.     

Combined penetrating keratoplasty and vitreoretinal surgery with silicone oil: a 1-year follow-up

BACKGROUND. The aim of this study was to assess the functional outcome of eyes with corneal and vitreoretinal diseases following combined surgical procedures (pars plana vitrectomy with temporary keratoprosthesis, vitreoretinal surgery, and penetrating keratoplasty with intravitreal silicone oil tamponade) and to evaluate the factors preserving the clarity of grafts. METHODS. Fifty-three eyes from 49 consecutive patients, operated on between 1991 and 1998 and followed up for at least 12 months, were evaluated retrospectively. The evaluation focused on ocular history, visual acuity (VA), intraocular pressure, anterior and posterior anatomical outcome, and complications. RESULTS. The average follow-up was 28.4 months+/-18.8 months (range 12-84 months); at the final visit 58% of the eyes had better VA, and 73% had equal or better acuity; the cornea remained clear in 68% of the eyes. A decrease in VA was caused by: loss of light perception in 2 eyes, one of which had to be enucleated because of painful phthisis; hypotony or phthisis in 23 eyes; recurrent retinal detachment in 4 eyes that were operated because of trauma; and immunological reaction in 2 eyes. Preoperative factors that contributed to a clear graft, but were not significant, were: lack of trauma (74%), no actual silicone oil filling (78%), preoperative VA of hand movement or better (79%), and attached retina (73%). Further surgery was needed in 55% of cases. The risk of transplant failure was significantly lower in eyes that did not undergo additional surgery (p=0.0001). CONCLUSION. The long-term results of combined surgery with penetrating keratoplasty in eyes that would otherwise be untreatable is often limited by anterior segment complications, mainly secondary graft failure and ciliary body malfunction. For optimal preservation of graft clarity, stable ocular status should be achieved before transplantation to minimize the necessity for further surgery.     

Temporal bone imaging using digital volume tomography and computed tomography: a comparative cadaveric radiological study

Purpose  

The aim of the present study was to analyze the diagnostic value of some temporal bone structures, e.g., ossicular chain, with digital volume tomography (DVT) compared with computed tomography (CT).     

Dopamine drives left‐hemispheric lateralization of neural networks during human speech

Although the concept of left‐hemispheric lateralization of neural processes during speech production has been known since the times of Broca, its physiological underpinnings still remain elusive. We sought to assess the modulatory influences of a major neurotransmitter, dopamine, on hemispheric lateralization during real‐life speaking using a multimodal analysis of functional MRI, intracranial EEG recordings, and large‐scale neural population simulations based on diffusion‐weighted MRI. We demonstrate that speech‐induced phasic dopamine release into the dorsal striatum and speech motor cortex exerts direct modulation of neuronal activity in these regions and drives left‐hemispheric lateralization of speech production network. Dopamine‐induced lateralization of functional activity and networks during speaking is not dependent on lateralization of structural nigro‐striatal and nigro‐motocortical pathways. Our findings provide the first mechanistic explanation for left‐hemispheric lateralization of human speech that is due to left‐lateralized dopaminergic modulation of brain activity and functional networks.     

The effect of cortico-spinal tract damage on primary sensorimotor cortex activation after rehabilitation therapy

Recently, it was shown that patients have different functional activation patterns within affected primary sensorimotor cortex (SMC) after intensive rehabilitation therapy. This individual difference was supposed to depend on the integrity of the cortico-spinal fibres from the primary motor cortex. In this study, we considered whether patients with different fMRI activation patterns after intensive rehabilitation therapy suffered from different cortico-spinal fibre lesions. To comprehend this circumstance a lesion subtraction analysis was used. To verify these results with the use of transcranial magnetic stimulation motor evoked potentials was also derived. Patients were treated after a modified version of constraint-induced movement therapy (modCIMT; 3 h daily for 4 weeks). Increased and decreased SMC activation showed similar individual patterns as described previously. These activation differences depend on the integrity of the cortico-spinal tract, which was measured via lesion subtraction analysis between patient groups, and was supported by affected motor evoked potentials.     

Activation changes in sensorimotor cortex during improvement due to CIMT in chronic stroke

Purpose: The integrity of the pyramidal tract (PT) does not seem to influence clinical improvement after two weeks of Constraint-Induced Movement Therapy (CIMT). However, when PT is intact, improvement is associated with a decrease of fMRI-activation in primary sensorimotor cortex (SMC) and when affected, with an increase of activation in SMC. The aim was to observe the long-term effect of CIMT, depending on the integrity of the PT, and to correlate improvement with changes in fMRI-activation. Subjects and methods: Twelve new chronic stroke patients were treated with CIMT and integrity of PT was measured with transcranial magnetic stimulation. Before therapy, after therapy, and after 6 months, changes in motor function were correlated with differential and percent fMRI signal changes. Results: All patients improved after two weeks of therapy, but only those with intact PT maintained improvement after 6 months. When PT was intact, improvement correlated with first a decrease of activation in SMC and after 6 months with an increase. When PT was affected, improvement consistently correlated with an increase in a lateral extension of SMC. Percent changes of activation were surrounded by differential changes. Conclusions: An intact PT might be advantageous for lasting improvement after CIMT and subregions in the SMC seem to behave differently during recovery.     

A prognosis based classification of undifferentiated uterine sarcomas: Identification of mitotic index,hormone receptors and YWHAE‐FAM22 translocation status as predictors of survival

Undifferentiated uterine sarcomas (UUS) are rare tumors with a heterologous biology and a poor prognosis. The goal of this study was to examine clinicopathology, biomarkers and YWHAE‐FAM22 translocation status, in the prognosis of these tumors. Twenty‐six cases of UUS were included. All original slides were rereviewed and age at diagnosis, tumor stage, “Kurihara” diagnosis, mitotic index, presence of necrosis and grade of nuclear atypia were recorded. Additionally, a tissue microarray was constructed from 22 of the cases, and the protein biomarkers P53, P16, Ki‐67, Cyclin‐D1, ER, PR and ANLN were evaluated by immunohistochemistry. All tumors were evaluated for the presence of a YWHAE‐FAM translocation; the translocation was demonstrated in the three Cyclin‐D1 positive tumors. Follow‐up data in the form of overall survival were available on all patients. These tumors could be divided into two prognostic groups, a high mitotic index group (10 cases, M = 36.8, SD = 5.4) and a low mitotic index group (16 cases, M = 8.7, SD = 5.8). These two groups showed a statistically significant difference in prognosis. The expression of ER, PR or presence of the YWHAE‐FAM22 translocation correlated with low mitotic index and an additionally improved prognosis, although the number of cases was small. These results indicate that UUS can be divided into two prognostic groups using mitotic index as a primary criteria, followed by expression of either ER, PR or the presence of a YWHAE‐FAM22 translocation as a secondary criteria. This study demonstrates the presence of statistically significant prognostic subgroups within UUS, and provides treatment insights.