Cross-Linking-Mass Spectrometry Studies of Cholesterol Interactions with Human α1 Glycine Receptor.

The glycine receptor (GlyR) belongs to a superfamily of pentameric ligand-gated ion channels (pLGICs) that mediate fast neurotransmission. GlyR typically modulates inhibitory transmission by antagonizing membrane depolarization through anion influx. Allosteric interactions between the receptor and its lipid surroundings affect receptor function, and cholesterol is essential for pLGIC activity. Cholesterol at compositions below ∼33 mol percent has been shown to have negligible chemical activity, suggesting that specific interactions between membrane proteins and cholesterol become significant only at concentrations above this stoichiometric threshold. Human α1 GlyR was purified from baculovirus infected insect cells and reconstituted in unilamellar vesicles at cholesterol/lipid ratios above and below the cholesterol activity threshold with equivalent aliquots of azi-cholesterol, a photoactivatable nonspecific cross-linker. After photoactivation, cross-linked cholesterol-GlyR was trypsinized and mass fingerprinted. Mass shifted peptides containing cholesterol were identified by electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF MS), and sites of direct covalent attachment to peptides were refined by targeted MS/MS. Differential patterns of dozens of cholesterol-GlyR cross-links were identified in these comparative studies, with sites of cross-linking found primarily in the fourth transmembrane helix and extramembranous connecting loops and mapping the lipid-accessible surface of the receptor. Unique cross-linking observed in both reduced and elevated cholesterol composition suggests different apo-state structural conformations of GlyR as a function of cholesterol concentration and, in the latter studies, identified potential specific binding sites for cholesterol in the receptor.

The role of 5-aminolevulinic acid in brain tumor surgery: a systematic review.

Recently, 5-aminolevulinic acid (5-ALA) has been utilized as an adjuvant to the surgical resection of primary brain tumors and metastases. We conducted a systematic review of the literature to further understand the role of 5-ALA in neurosurgery. Our goal was to identify the utility of 5-ALA during resection by evaluating its sensitivity and specificity for different tumor types, as well as the extent of tumor resection achieved while using 5-ALA. A search of the literature was conducted using the PubMed database for the period January 1990 through May 2014. Surgical series in which 5-ALA was used for brain neoplasm resections were evaluated for tumor histology, sensitivity, specificity, extent of resection, complications, and outcomes. Twenty-two series, involving 1163 patients, were included in our review. 5-ALA sensitivity was highest in high-grade gliomas (85 %) and meningiomas (81 %). 5-ALA specificity was high in meningiomas (100 %), as well as metastases (84 %) and high-grade gliomas (82 %). Gross total resection (GTR) was achieved using 5-ALA in 66.2 % of all gliomas and 69.6 % of meningiomas, regardless of histological subtype. 5-ALA may be a useful tool in increasing the extent of resection and achieving GTR in intracranial tumors. The resection of tumors for which 5-ALA has high sensitivity and specificity, such as high-grade gliomas, may lead to an increase in extent of resection when compared to operations using only standard white light. Further evidence for the use of 5-ALA in meningiomas and certain subtypes of metastases may be needed to qualify its efficacy.

Yield and utility of routine postoperative imaging after resection of brain metastases.

Magnetic resonance imaging (MRI) or computerized tomography (CT) is routinely performed after resection of brain metastases (BrM), regardless of whether there are specific clinical concerns about residual tumor or potential complications. Routine imaging studies contribute a significant amount to the cost of medical care, and their yield and utility are unknown. An IRB-approved retrospective chart review study was performed to analyze all craniotomies for BrM performed at our institution from 2005 to 2012. Descriptive statistics were used to quantify the yield of postoperative imaging. 218 consecutive patients underwent 226 craniotomies for BrM. In 21 cases, new or worsened neurologic deficits occurred after surgery (9.0%), and 19 of the 21 underwent postoperative imaging. 9 of the 19 patients (47%) had significant findings on postoperative imaging, and 2 patients required reoperation. 201 patients had no new neurologic deficits (91%), and 23 of these patients had no postoperative imaging. Of the 178 remaining patients, 160 underwent postoperative MRI and 18 underwent postoperative CT. 9 patients (5.1%) had unexpected adverse imaging findings; 6 had small stroke, 1 had a subdural hemorrhage and 2 had possible or definite venous sinus occlusion. None of the imaging findings led to changes in management. 182 patients underwent imaging appropriate to detect residual tumor (177 gadolinium enhanced MRI and 5 contrast enhanced CT). Of these patients, 16 were known to have small residual tumors based on intraoperative findings. Of the remaining 166 patients felt to have had gross total tumor resection, 9 (5.4%) were found to have a small amount of residual tumor on postoperative imaging; no patient had a change in treatment plan as a result. Routine postoperative imaging in patients undergoing craniotomy for BrM has a very low yield and may not be appropriate in the absence of new neurologic deficits, or specific clinical concerns about large amounts of residual tumor or intraoperative complications.

Predictors of long-term survival in patients with glioblastoma multiforme: advancements from the last quarter century.

Over the last quarter century there has been significant progress toward identifying certain characteristics and patterns in GBM patients to predict survival times and outcomes. We sought to identify clinical predictors of survival in GBM patients from the past 24 years. We examined patient survival related to tumor locations, surgical treatment, postoperative course, radiotherapy, chemotherapy, patient age, GBM recurrence, imaging characteristics, serum, and molecular markers. We present predictors that may increase, decrease, or play no significant role in determining a GBM patient's long-term survival or affect the quality of life.

Extracranial glioblastoma in transplant recipients.

PURPOSE: Traditionally, gliomas are considered to be confined to the central nervous system. The shortage of solid donor organs resulted in consideration of organs from patients with primary malignancy such as glioblastoma multiforme (GBM) for transplantation into patients suffering from end-stage organ disease. METHODS: We performed a PubMed search including all studies that documented patient demographics, pre- and post-transplantation conditions as well as time to metastasis and overall survival in recipients of organ transplants from donors suffering from GBM. RESULTS: A total of 11 studies with 11 patients were included in this review. Three patients had liver, three had kidney, and five had lung transplantation. For kidney transplants, average time to metastasis was 17.3 months post-surgery. The average follow-up time was 32.3 months, and all patients were doing well. All liver transplant recipients succumbed due to GBM metastasis. The average survival was 7 months for all three patients. For lung-receiving patients, two patients died at an average of 9.5 months post-transplantation, with a mean time to metastasis of 9 months. Two patients were doing well at 17- and 20-month follow-up. One patient was diagnosed with metastasis 12 months after transplantation, but no follow-up data were provided. CONCLUSIONS: These studies emphasize the disadvantage of transplanting an organ of an individual with GBM. However, it should be noted that these cases do not make up a large percentage of overall transplantations, and donors with primary central nervous system malignancies also do not represent the whole pool of organs available.

3 cases of primary intracranial hemorrhage associated with "Molly", a purified form of 3,4-methylenedioxymethamphetamine (MDMA).

3,4-Methylenedioxymethamphetamine (MDMA, or "Ecstasy" in tablet form) is a powerful sympathomimetic drug that is commonly perceived as safer than other stimulants such as methamphetamine or cocaine. "Molly" is a purified form of MDMA that is perceived by users as being even safer, as it is free of adulterants such as methamphetamine. Previously, all reports of intracranial hemorrhages in MDMA abusers were associated with coingestion of other sympathomimetic drugs, or with pre-existing cerebrovascular lesions. We describe a series of three young, otherwise healthy patients with various types of intracranial hemorrhages associated with "Molly" ingestion. All three patients underwent extensive workup including catheter angiography that did not demonstrate aneurysm, arteriovenous malformation, or vasculitis. We suggest that even the purified form of MDMA can cause serious intracranial hemorrhagic complications and should not be thought of as a safe recreational drug.