Binding characteristics of 9-fluoropropyl-(+)-dihydrotetrabenzazine (AV-133) to the vesicular monoamine transporter type 2 in rats

The vesicular monoamine transporter type 2 (VMAT2) is highly expressed in pancreatic β-cells and thus has been proposed to be a potential target for measuring β-cell mass (BCM) by molecular imaging. C-11- and F-18-labeled tetrabenazine derivatives targeting VMAT2 have shown some promising results as potential biomarkers for BCM. In the present study, we examined the binding characteristics of 9-fluoropropyl-(+)-dihydrotetrabenzazine ([¹⁸F]AV-133), a potential PET tracer for BCM imaging, in rat pancreas and rat brain.MethodsPancreatic exocrine cells and pancreatic islet cells were isolated and purified from Sprague-Dawley rats. Membrane homogenates, prepared from both pancreatic exocrine and islet cells as well as from brain striatum and hypothalamus regions, were used for in vitro binding studies. In vitro and ex vivo autoradiography studies with [¹⁸F]AV-133 were performed on rat brain and rat pancreas sections. Immunohistochemistry studies were performed to confirm the distribution of VMAT2 on islet β-cells.ResultsExcellent binding affinities of [¹⁸F]AV-133 were observed in rat striatum and hypothalamus homogenates with K_d values of 0.19 and 0.25 nM, respectively. In contrast to single-site binding observed in rat striatum homogenates, rat islet cell homogenates showed two saturable binding sites (site A: K_d=6.76 nM, B_max=60 fmol/mg protein; site B: K_d=241 nM, B_max=1500 fmol/mg protein). Rat exocrine pancreas homogenates showed only a single low-affinity binding site (K_d=209 nM), which was similar to site B in islet cells. In vitro autoradiography of [¹⁸F]AV-133 using frozen sections of rat pancreas showed specific labeling of islets, as evidenced by co-localization with anti-insulin antibody. Ex vivo VMAT2 pancreatic autoradiography in the rat, however, was not successful, in contrast to the excellent ex vivo autoradiography of VMAT2 binding sites in the brain. In vivo/ex vivo islet labeling may be complicated by the presence of the low-affinity/high-capacity site B binding in rat pancreas.Conclusions[¹⁸F]AV-133 is an excellent imaging agent for mapping VMAT2 sites in rat brain and specifically binds rat islet cells in vitro and postmortem. Additional optimization may be required to achieve ex vivo islet β-cell labeling in rats.     

Comorbid migraine is associated with a negative impact on quality of life in patients with major depression

This study investigated the impact of migraine on health-related quality of life (HRQoL) among patients with major depressive disorder (MDD). We prospectively enrolled 151 consecutive psychiatric out-patients meeting DSM-IV criteria for MDD. Migraine and other headache types were diagnosed based on the International Classification of Headache Disorders, 2nd edition (2004). The Short Form-36 (SF-36) was administered as a generic instrument of HRQoL. Among 151 patients with MDD, migraine ( N  = 73, 48.3%) was very common. Comorbidity of migraine predicted a significantly negative impact on all physical subscales and vitality but not on the other mental subscales of the SF-36 after controlling for depression, age and gender. The presence of migraine should be considered as an important physical symptom in clinic-based MDD samples. Simultaneous management of depression and severe headaches, especially migraine, might improve HRQoL in patients with MDD.     

Characteristics of Chinese patients with symptomatic Brugada syndrome in Taiwan

Since 1992, the Brugada syndrome has been increasingly recognized worldwide, although its incidence and distribution remain unclear. In Asia, several cases have been reported in Japan, Thailand, Singapore, and Vietnam. However, little information is available from the Chinese population. Since June 1997, we have identified 10 patients with the diagnosis of the Brugada syndrome from six hospitals in Taiwan. All patients were male with the mean age of 46 +/- 7 years (range 36-61). They all had a normal chemistry profile, coronary angiography and echocardiography. Clinical presentations varied from seizure and syncope to sudden cardiac death. MRI and ultrafast CT of the heart did not show any abnormalities. Sustained ventricular tachycardia/ventricular fibrillation (VF) was induced in 7 of 8 patients who underwent an electrophysiologic study. The pharmacological provocation test was positive in 4 of 5 patients. One of the 4 patients who had a genetic study showed SCN5A gene mutation. An implantable cardioverter defibrillator (ICD) was implanted in 8 patients. During a mean follow-up of 29 +/- 17 months (range 2-54), 3 of 8 patients who had an ICD received appropriate ICD discharges after implantation. These 3 patients who were subsequently treated with antiarrhythmic agents have had no further recurrent ICD discharges. Two patients who refused ICD implantation are alive and well without taking antiarrhythmic agents. Our study showed that the clinical characteristics of our patients are similar to those described in the literature and that ICD is an effective treatment modality for patients with recurrent VF. However, antiarrhythmic agents may be beneficial for suppressing arrhythmia recurrences in selected patients.     

功能性胃肠病的根源——脑肠轴神经系统记忆假说

功能性胃肠病(functionalgastrointestinaldisorders,FGID)以消化道动力与内脏感觉异常为主要病理生理特征并有多种症状重叠、多变或相互转换以及反复发作、较难治愈等特点;其病因和发病机制目前仍未完全清楚.本文将大脑记忆外延提出FGID的根源是脑肠轴神经系统记忆的假说,并用这个假说解释说明FGID的各种特点,以及治疗FGID的思路和方法.     

Psychopathology in individuals with post-traumatic headaches and other pain types

In this study, the psychological functioning of patients with chronic post-traumatic headache (PTH), chronic combination headache and chronic low back pain without headache, whose time of onset was similar, and a matched group of controls was investigated. The Symptom Checklist 90-Revised (SCL-90-R), State-Trait Anger Expression Inventory (STAXI), State-Trait Anxiety Inventory, Form Y (STAI-Y), and Beck Depression Inventory (BDI) were used to assess the degree of psychopathology. A MANOVA test indicated highly significant differences between groups. In general, the pain groups fell along a continuum with PTH subjects demonstrating the highest elevations, back pain subjects demonstrating the next highest elevations, and combination subjects demonstrating fewer elevations. A cluster analysis indicated that findings were best classified into four clusters, but no one pain diagnosis predominated in any cluster. Eighty-nine percent of controls were assigned to clusters 1 or 2, which revealed essentially normal scores on all tests. It is suggested that while chronic pain patients demonstrate more psychopathology than non-pain controls, a variety of coping styles exists within each pain group independent of diagnostic categorization.