Tyler M. Berzin

Microvascular injury and blood–brain barrier leakage in Alzheimer's disease

Thinning and discontinuities within the vascular basement membrane (VBM) are associated with leakage of the plasma protein prothrombin across the blood-brain barrier (BBB) in Alzheimers disease (AD). Prothrombin immunohistochemistry and ELISA assays were performed on prefrontal cortex. In severe AD, prothrombin was localized within the wall and neuropil surrounding microvessels. Factor VIII staining in severe AD patients indicated that prothrombin leakage was associated with shrinkage of endothelial cells. ELISA revealed elevated prothrombin levels in prefrontal cortex AD cases that increased with the Braak stage (Control=1.39, I-II=1.76, III-IV=2.28, and V-VI=3.11 ng prothrombin/mg total protein). Comparing these four groups, there was a significant difference between control and Braak V-VI (p=0.0095) and also between Braak stages I-II and V-VI (p=0.0048). There was no significant difference in mean prothrombin levels when cases with versus without cerebral amyloid angiopathy (CAA) were compared (p-value=0.3627). When comparing AD patients by APOE genotype (ApoE3,3=2.00, ApoE3,4=2.49, and ApoE4,4=2.96 ng prothrombin/mg total protein) an analysis of variance indicated a difference between genotypes at the 10% significance level (p=0.0705). Tukeys test indicated a difference between the 3,3 and 4,4 groups (p=0.0607). These studies provide evidence that in advanced AD (Braak stage V-VI), plasma proteins like prothrombin can be found within the microvessel wall and surrounding neuropil, and that leakage of the blood-brain barrier may be more common in patients with at least one APOE4 allele.

Agrin and microvascular damage in Alzheimer’s disease

Abstract Heparan sulfate proteoglycans (HSPGs) are ubiquitously present within the perivascular basement membrane, and have been shown to be altered in patients with Alzheimer’s Disease (AD). Although the HSPG agrin clearly orchestrates the differentiation of the neuromuscular junction, its role in the brain remains unclear. Growing evidence suggests that agrin may be an important vascular basement membrane (VBM)-associated HSPG. In previous studies, we demonstrated that agrin is present throughout the brain microvasculature, as well as in neuronal cell bodies. AD brains exhibited fragmentation of VBM-associated agrin. Agrin immunoreactivity was also seen within senile plaques and neurofibrillary tangles. These changes were accompanied by the appearance of an additional pool of insoluble agrin. In the present study, we provide further evidence for microvascular damage in AD, by examining the distribution of agrin and laminin within the VBM, and by measuring the agrin concentration within hippocampus and prefrontal cortex. Furthermore, we assessed blood-brain-barrier (BBB) leakage by examining the perivascular distribution of prothrombin immunoreactivity. Soluble agrin levels were increased approximately 30% in Braak stage III–VI AD patients relative to age-matched controls. Furthermore, agrin and laminin exhibited identical patterns of VBM fragmentation in AD and colocalized with beta-amyloid in senile plaques. Microvascular changes were associated with the appearance of perivascular prothrombin immunoreactivity. Our data suggest that agrin is an important VBM-associated HSPG in the brain and that agrin levels are altered in association with microvascular damage in AD.

Human Choroid Plexus Growth Factors: What Are the Implications for CSF Dynamics in Alzheimer's Disease?

The choroid plexus plays a key role in supporting neuronal function by secreting cerebrospinal fluid (CSF) and may be involved in the regulation of various soluble factors. Because the choroid plexus is involved in growth factor secretion as well as CSF dynamics, it is important to understand how growth factors in CSF interact with the brain parenchyma as well as with cells in direct contact with the flowing CSF, i.e., choroid plexus and arachnoid villi. While the existence of growth factors in the choroid plexus has been documented in several animal models, the presence and distribution of growth factors in the human choroid plexus has not been extensively examined. This study describes the general distribution and possible functions of a number of key proteins in the human choroid plexus and arachnoid villi, including basic fibroblast growth factor, FGF receptor, and vascular endothelial growth factor. FGF and VEGF could both be readily demonstrated in choroid plexus epithelial cells. The presence of FGF and VEGF within the choroid plexus was also confirmed by ELISA analysis. Since Alzheimers disease (AD) is known to be associated with a number of growth factor abnormalities, we examined the choroid plexus and arachnoid villi from AD patients. Immunohistochemical studies revealed the presence of FGF and VEGF within the AD choroid plexus and an increased density of FGFr in both the choroid plexus and the arachnoid villi of AD patients. No qualitative changes in the distribution of FGF and VEGF were observed in the AD choroid plexus. The appearance of FGFr in AD arachnoid was associated with robust amyloid and vimentin immunoreactivity. These findings confirm the presence of FGF and VEGF within the normal and AD choroid plexus and suggest that the alteration of growth factors and their receptors may contribute to the pathogenesis of the hydrocephalus ex vacuo that is characteristically seen in AD.

A prospective evaluation of fatty pancreas by using EUS

BACKGROUND Fatty liver is associated with obesity, diabetes, hyperlipidemia, and the metabolic syndrome. The pathophysiology of fatty pancreas is poorly understood, but it may be closely related to fatty liver. OBJECTIVE The aim of our study was to determine the prevalence of fatty pancreas and risk factors associated with its development. DESIGN Prospective, single center study. SETTING Tertiary-care academic medical center. PATIENTS This study involved 250 consecutive patients referred for EUS examination. INTERVENTION All patients undergoing EUS at our institution were prospectively identified. Information regarding demographics, tobacco use, alcohol use, blood test results, and comorbidities were collected before EUS. Pancreatic echogenicity was graded in comparison to the spleen at the time of EUS by using an a priori specified grading scheme. MAIN OUTCOME MEASUREMENTS Prevalence of fatty pancreas and factors associated with its development. RESULTS During the study period, 250 consecutive patients were prospectively enrolled. The prevalence of fatty pancreas was 27.8% (95% CI, 22.1-34.1). Fatty liver was seen in 22.6% of patients. Factors associated with fatty pancreas on univariate analysis were increasing body mass index (BMI) (P=.004), fatty liver (P<.0001), hyperlipidemia (P=.04), and the metabolic syndrome (odds ratio [OR] 3.13, P=.004). The presence of any metabolic syndrome components, that is, BMI≥30, hyperlipidemia, diabetes, or hypertension, increased the prevalence of fatty pancreas by 37% (OR 1.37, P=.01). Factors independently associated with fatty pancreas on multivariate analysis were increasing BMI (OR 1.05, P=.03) and fatty liver (OR 3.61, P<.001). We found no association between fatty pancreas and chronic pancreatitis or adenocarcinoma of the pancreas. LIMITATIONS Single institution study. All patients were referred for EUS, which limits generalizability. Lack of histological confirmation of pancreatic fat. CONCLUSION We found a strong association between fatty pancreas and the metabolic syndrome.

Effect of APOE genotype on microvascular basement membrane in Alzheimer's disease

APOE4 homozygosity has been associated with an increased risk of sporadic Alzheimers disease through a mechanism, which has yet to be defined. Recent evidence has suggested that microvascular basement membrane injury may be a critical factor in the pathogenesis of AD-related dementia. In previous studies, we have shown that the synaptic organizing protein agrin can be found in neurons, and is a major component of the brain microvascular basement membrane. Here, we compare the basement membrane surface area of cortical microvasculature in AD brains by staining with an anti-agrin antibody. Quantitative morphometric analysis was used to determine the mean basement area (micro(2)) of prefrontal cortical microvessels. An average of 10 capillaries was measured in each of 35 cases of AD genotyped for APOE status. APOE4,4 homozygotes had smaller capillary basement membrane areas (17.4 micro(2))+/-6.2) than APOE3,3 homozygotes (26.9 micro(2)+/-6.5), p<0.001. The capillary basement membrane areas (CBMA) of heterozygotes APOE3,4 did not differ significantly from APOE3,3 or APOE4,4. Braak stage did not contribute significantly to CBMA. However, a preliminary analysis suggests an interaction between APOE4,4 and Braak V-VI producing smaller CBMA, a finding which needs to be confirmed with a larger sample. These data support the hypothesis that APOE4,4 is associated with thinning of the microvascular basement membrane in Alzheimers disease.

Prevalence of Primary Fungal Infections in Necrotizing Pancreatitis

Background/Aims: Prophylactic use of carbapenems (meropenem and imipenem) and other broad-spectrum antibiotics in necrotizing pancreatitis has been suggested as a risk factor for pancreatic fungal infections. The aim of our study was to determine the prevalence of primary fungal infections and the pattern of antibiotic use in necrotizing pancreatitis at our institution. Methods: Records on 689 consecutive patients with acute pancreatitis between 2000 and 2004 were reviewed. Necrotizing pancreatitis was identified by contrast-enhanced computed tomography (CT) scan. Data on antibiotic usage were collected and microbiologic data obtained from radiologic, endoscopic, and surgical interventions (pancreatic aspiration, drain placement or debridement) were reviewed for evidence of fungal infection. Pancreatic fungal infections were classified as primary if the positive culture was obtained at the time of initial intervention. Results: Among 64 patients with necrotizing pancreatitis, there were no cases of primary pancreatic fungal infections and 7 cases (11%) of secondary pancreatic fungal infections. Fifteen patients (23%) developed pancreatic bacterial infections. Among 62 patients with necrotizing pancreatitis in whom antibiotic exposure was known, 45% received carbapenems for a median duration of only 6 days, and 84% received non-carbapenem antibiotics for a median duration of 14 days. Conclusion: Limited use and short duration of carbapenem therapy may be factors contributing to the absence of primary fungal infections in our study.

Propofol versus traditional sedative agents for advanced endoscopic procedures: A meta-analysis

The optimum method for sedation for advanced endoscopic procedures is not known. Propofol deep sedation has a faster recovery time than traditional sedative agents, but may be associated with increased complication rates. The aim of the present study was to pool data from all available studies to systematically compare the efficacy and safety of propofol with traditional sedative agents for advanced endoscopic procedures.

Initial experience with a novel EUS-guided core biopsy needle (SharkCore): results of a large North American multicenter study.

Background and aims: The ability to safely and effectively obtain sufficient tissue for pathologic evaluation by using endoscopic ultrasound (EUS) guidance remains a challenge. Novel designs in EUS needles may provide for improved ability to obtain such core biopsies. The aim of this study was to evaluate the diagnostic yield of core biopsy specimens obtained using a novel EUS needle specifically designed to obtain core biopsies. Patients and methods: Multicenter retrospective review of all EUS-guided fine-needle biopsies obtained using a novel biopsy needle (SharkCore FNB needle, Medtronic, Dublin, Ireland). Data regarding patient demographics, lesion type/location, technical parameters, and diagnostic yield was obtained. Results: A total of 250 lesions were biopsied in 226 patients (Median age 66 years; 113 (50 %) male). Median size of all lesions (mm): 26 (2 – 150). Overall, a cytologic diagnosis was rendered in 81 % specimens with a median number of 3 passes. When rapid onsite cytologic evaluation (ROSE) was used, cytologic diagnostic yield was 126/149 (85 %) with a median number of 3 passes; without ROSE, cytologic diagnostic yield was 31/45 (69 %, P = 0.03) with a median number of 3 passes. Overall, a pathologic diagnosis was rendered in 130/147 (88 %) specimens with a median number of 2 passes. Pathologic diagnostic yield for specific lesion types: pancreas 70/81 (86 %), subepithelial lesion 13/15 (87 %), lymph node 26/28 (93 %). Ten patients (10/226, 4 %) experienced adverse events: 4 acute pancreatitis, 5 pain, 1 fever/cholangitis. Conclusions: Initial experience with a novel EUS core biopsy needle demonstrates excellent pathologic diagnostic yield with a minimum number of passes.

A meta-analysis on efficacy and safety: single-balloon vs. double-balloon enteroscopy.

Background and aim: Double-balloon enteroscopy (DBE) and single-balloon enteroscopy (SBE) are new techniques capable of providing deep enteroscopy. Results of individual studies comparing these techniques have not been able to identify a superior strategy. Our aim was to systematically pool all available studies to compare the efficacy and safety of DBE with SBE for evaluation of the small bowel. Methods: Databases were searched, including PubMed, Embase, and the Cochrane Central Register of Controlled Trials. The main outcome measures were complete small-bowel visualization, diagnostic yield, therapeutic yield, and complication rate. Statistical analysis was performed using Review Manager (RevMan version 5.2). Meta-analysis was performed using fixed-effect or random-effect methods, depending on the absence or presence of significant heterogeneity. We used the χ2 and I2 test to assess heterogeneity between trials. Results were expressed as risk ratios (RR) or mean differences with 95% confidence intervals (CI). Results: Four prospective, randomized, controlled trials with a total of 375 patients were identified. DBE was superior to SBE for visualization of the entire small bowel [pooled RR = 0.37 (95% CI: 0.19–0.73; P = 0.004)]. DBE and SBE were similar in ability to provide diagnosis [pooled RR = 0.95 (95% CI: 0.77–1.17; P = 0.62)]. There was no significant difference between DBE and SBE in therapeutic yield [pooled RR = 0.78 (95% CI: 0.59–1.04; P = 0.09)] and complication rate [pooled RR = 1.08 (95% CI: 0.28–4.22); P = 0.91]. Conclusions: DBE was superior to SBE with regard to complete small bowel visualization. DBE was similar to SBE with regard to diagnostic yield, ability to provide treatment and complication rate, but these results should be interpreted with caution as they is based on very few studies and the overall quality of the evidence was rated as low to moderate, due to the small sample size.

Endoscopic Ultrasound–guided Pancreatic Fiducial Placement: How Important Is Ideal Fiducial Geometry?

Objective Image-guided radiation therapy allows precise tumor targeting using real-time tracking of radiopaque fiducial markers. To enable appropriate tracking, it is recommended to place fiducials with “ideal fiducial geometry” (IFG). Our objectives were to determine the proportion of patients in whom IFG can be achieved when fiducials are placed by endoscopic ultrasound (EUS) and surgery and to determine if attaining IFG is necessary for delivering radiation. Methods This single-center retrospective cohort study included 77 patients with biopsy-proven advanced pancreatic cancer who underwent either EUS-guided or laparotomy/laparoscopy-assisted fiducial placement between September 2005 and July 2009. Results Gold fiducials were implanted by EUS in 39 patients (51%) and by surgery in 38 patients (49%). The proportion of patients with IFG was significantly higher for surgical placement [18/38, 47%; 95% confidence interval (CI), 32%–63%] compared with EUS-guided placement (7/39, 18%; 95% CI, 8%–32%), P = 0.0011. However, fiducial tracking was successfully used for Cyberknife therapy in 35 (90%) of 39 (95% CI, 77%–97%) patients in the EUS group compared with 31 (82%) of 38 (95% CI, 67%–92%) patients in the surgery group. There were 5 procedure-related complications in the EUS group. Conclusions Achieving IFG appears unnecessary for successful tracking and delivery of radiation.