Alex Braun

Anatomic analysis of blood vessels in germinal matrix, cerebral cortex, and white matter in developing infants

The germinal matrix (GM) located in the thick subependymal cell layer of the thalamostriate groove is a major site of cerebral hemorrhage in premature infants. Comparing the morphology of vasculature among GM, gray and white matter of the brain may help in understanding the pathogenesis of GM hemorrhage and also of periventricular leukomalacia. The objective of the present study was to determine the morphology of blood vessels in the GM, gray matter, and white matter and to examine maturational changes in the morphology of these vessels as a function of gestational age. We measured vessel density, percentage of blood vessel area, mean surface area, length, breadth, perimeter, radius, and shape of blood vessels in coronal sections of the GM, gray matter, and white matter in postmortem human brain samples for 17 fetuses and premature infants of gestational age 16–40 wk and 2 adults. We performed immunohistochemical staining using anti-laminin primary antibody, confocal microscopy to acquire images, and analysis using Metamorph version 6.1. Vessel density and the percentage of blood vessel area increased as a function of gestational age in the GM, gray matter, and white matter (p < 0.001 each). The blood vessel density and the percentage of blood vessel area were largest in the GM followed by gray matter and then white matter in all of the gestational age categories (p < 0.001 for all comparisons). Increased vascularity of the GM compared with gray and white matter may play a role in GM hemorrhage, whereas a relatively low vascularity of white matter may increase the propensity for the occurrence of periventricular leukomalacia in premature infants

Consequences of Intraventricular Hemorrhage in a Rabbit Pup Model

Background and Purpose— Intraventricular hemorrhage (IVH) is a common complication of prematurity that results in neurological sequelae, including cerebral palsy, posthemorrhagic hydrocephalus, and cognitive deficits. Despite this, there is no standardized animal model exhibiting neurological consequences of IVH in prematurely delivered animals. We asked whether induction of moderate-to-severe IVH in premature rabbit pups would produce long-term sequelae of cerebral palsy, posthemorrhagic hydrocephalus, reduced myelination, and gliosis. Methods— The premature rabbit pups, delivered by cesarean section, were treated with intraperitoneal glycerol at 2 hours postnatal age to induce IVH. The development of IVH was diagnosed by head ultrasound at 24 hours of age. Neurobehavioral, histological, and ultrastructural evaluation and diffusion tensor imaging studies were performed at 2 weeks of age. Results— Although 25% of pups with IVH (IVH pups) developed motor impairment with hypertonia and 42% developed posthemorrhagic ventriculomegaly, pups without IVH (non-IVH) were unremarkable. Immunolabeling revealed reduced myelination in the white matter of IVH pups compared with saline- and glycerol-treated non-IVH controls. Reduced myelination was confirmed by Western blot analysis. There was evidence of gliosis in IVH pups. Ultrastructural studies in IVH pups showed that myelinated and unmyelinated fibers were relatively preserved except for focal axonal injury. Diffusion tensor imaging showed reduction in fractional anisotropy and white matter volume confirming white matter injury in IVH pups. Conclusion— The rabbit pups with IVH displayed posthemorrhagic ventriculomegaly, gliosis, reduced myelination, and motor deficits, like humans. The study highlights an instructive animal model of the neurological consequences of IVH, which can be used to evaluate strategies in the prevention and treatment of posthemorrhagic complications.

Astrocyte End-Feet in Germinal Matrix, Cerebral Cortex, and White Matter in Developing Infants

Astrocyte end-feet ensheathe blood vessels in the brain and are believed to provide structural integrity to the cerebral vasculature. We sought to determine in developing infants whether the coverage of blood vessels by astrocyte end-feet is decreased in germinal matrix (GM) compared with cerebral cortex and white matter (WM), which may cause fragility of the GM vasculature. Therefore, we evaluated the perivascular coverage by astrocyte end-feet in these areas. We double-labeled the brain sections with astroglial markers [glial fibrillary acidic protein (GFAP), aquaporin-4 (AQP4), and S-100β] and a vascular marker, laminin. Perivascular coverage by GFAP+ astrocyte end-feet increased consistently as a function of gestational age (GA) in cortex and WM from 19 to 40 wk. Compared with GFAP, AQP4+ astrocyte end-feet developed at an earlier GA, ensheathing about 63% of blood vessels for 23–40 wk in cortex, WM, and GM. Coverage by GFAP+ perivascular end-feet was decreased in GM compared with cortex and WM from 23 to 34 wk. There was no difference in the coverage by AQP4+ end-feet among the three areas in these infants. The expression of AQP4, a water channel molecule, in the astrocyte end-feet was not significantly different between premature and mature infants, suggesting similar risk of brain edema in preterm and term infants in pathologic conditions. More importantly, the lesser degree of GFAP expression in astrocyte end-feet of GM compared with cortex and WM may reflect a cytoskeletal structural difference that contributes to the fragility of GM vasculature and propensity to hemorrhage.

Development of tight junction molecules in blood vessels of germinal matrix, cerebral cortex, and white matter.

Tight junction (TJ) molecules confer cell-to-cell adhesion to endothelial cells and, thus, provide structural integrity to blood vessels. Therefore, decreased expression of these molecules may be a cause of germinal matrix (GM) fragility and their propensity to hemorrhage in premature infants. The objective of this study was to compare the expression of endothelial TJ molecules, including claudin-5, occludin, and junction adhesion molecules (JAM), among blood vessels of GM, cortex, and white matter for fetuses and premature infants of gestational age 16–40 wk, and to examine their maturational changes with advancing gestational age. We measured the expression of claudin-1, claudin-5, occludin, and JAM in GM, cortex, and white matter in postmortem brain samples. We performed immunohistochemical staining on brain sections and Western blot to quantify these molecules. We found that claudin-5, occludin, and JAM-1 were expressed as early as 16 wk in GM, cortex, and white matter. Claudin-1, JAM-2, and JAM-3 were not detected in the GM, cortex, and white matter. Claudin-5, occludin, and JAM-1 did not change significantly as a function of gestational age. There was no significant difference in the expression of these molecules in the vasculature of GM compared with cortex and white matter. Because the primary endothelial TJ molecules, including claudin-5, occludin, and JAM-1, are expressed as early as 16 wk in the blood brain barrier and since as they are not decreased in GM vasculature compared with cortex and white matter, they are unlikely to be responsible for GM fragility and vulnerability to hemorrhage in premature infants.

Endoscopic resection of an intraventricular dysembryoplastic neuroepithelial tumor of the septum pellucidum.

Tumors located in the region of the foramen of Monro often present with signs and symptoms of obstructive hydrocephalus. Various types of lesions occur in this location. We describe a case of a dysembryoplastic neuroepithelial tumor of the septum pellucidum presenting with obstructive hydrocephalus and its successful endoscopic excision. The surgical considerations and pathologic findings are discussed.

Recurrent nested stromal epithelial tumor of the liver with extrahepatic metastasis: case report and review of literature.

Nested stromal epithelial tumor is a recently described primary neoplasm of the liver. This tumor is characterized by well-demarcated nests of spindle and epithelioid cells with occasional calcification and bone formation. An association between these tumors and Cushing syndrome has been described. Herein we report a case of a recurrent nested stromal epithelial tumor of the liver in a 17-year-old female with aggressive clinical behavior and an extrahepatic lymph node metastasis. Also, we provide the first detailed clinical, histologic, immunohistochemical, and cytogenetic comparison of the original and recurrent tumors. Initially, the patient presented with Cushingoid symptoms and epigastric pain, radiating to her back. A computed tomographic (CT) scan revealed a large lesion in the liver. After a partial hepatectomy, the Cushingoid features were resolved. A year later, a CT scan revealed multiple lesions within the liver, and positron emission tomographic/CT imaging showed a hypermetabolic lymph node. The patient underwent a cadaveric liver transplant. Histologically, both the original and recurrent tumors had similar characteristics, with different immunoreactivity, correlating with the absence of systemic hormonal symptoms. Electron microscopy of the original neoplasm revealed an abundance of rough cytoplasmic reticulum and mitochondria. No evidence of endocrine differentiation was found. Cytogenetics of the primary tumor was complex with an abnormal hypotriploid karyotype. Our data indicate that patients with nested stromal epithelial tumor of the liver must be carefully followed with imaging to detect hepatic recurrence and extrahepatic metastases.

Deciphering the signaling pathways of cancer stem cells of glioblastoma multiforme: role of Akt/mTOR and MAPK pathways.

These findings emphasize that the mTOR pathway may contribute to maintenance of quiescence of CSCs, and provide a basis for manipulating CSCs in the treatment of GBM. Future research should focus on further defining the PI3K/Akt/mTOR molecular network in the regulation of stem cell quiescence and provide rationale for targeting the cancer-initiating cells of GBM.

Diagnostic challenges in Balamuthia mandrillaris infections

Balamuthia mandrillaris is an emerging cause of subacute granulomatous amebic encephalitis (GAE). The diagnosis of this infection has proven to be difficult and is usually made postmortem. Early recognition and treatment may offer some benefit. This report describes a previously healthy woman who died from GAE due to B. mandrillaris.

Development of integrins in the vasculature of germinal matrix, cerebral cortex, and white matter of fetuses and premature infants

Germinal matrix (GM) vasculature is selectively vulnerable to hemorrhage in premature infants during the first 48 hr of life. This is attributed to rapid angiogenesis of this brain region, resulting in formation of nascent vessels that show a paucity of pericytes and immaturity of extracellular matrix. Integrins are key regulators of angiogenesis and contribute to stabilization of cerebral vasculature by providing endothelial– and astrocyte–matrix adhesion. Therefore, we asked whether GM exhibited a distinct regional pattern of integrin expression that was dissimilar from that of the cerebral cortex and white matter in human fetuses and premature infants. To this end, we measured protein and gene expression of integrins in the GM, cortex, and white matter of human fetuses (15–22 weeks), premature infants (23–35 weeks), and mature infants (36–40 weeks). We found that protein levels of α5β1 integrin were greater in the GM than in the cortex or white matter by 1.6‐fold for both fetuses and premature infants. α5β1 integrin mRNA expression was higher in the GM than in the cortex or white matter by 2‐fold for fetuses but not for premature infants. αVβ3, αVβ5, αVβ8, and α4β1 integrin expression were comparable among GM, cortex, and white matter in fetuses and premature infants. Because α5β1 integrin is a central regulator of angiogenesis, its elevation in the GM of fetuses and premature infants indicates that this might be a key activator of endothelial proliferation in this brain region. We speculate that selective α5β1 integrin inhibition might suppress angiogenesis in the GM and thus prevent brain hemorrhage in premature infants.

Difference in Cryptococcus neoformans cellular and capsule size in sequential pulmonary and meningeal infection: a postmortem study

Cryptococcus neoformans is an encapsulated yeast that primarily causes a life-threatening meningoencephalitis in immunosuppressed individuals especially those with HIV/AIDS. Its main virulence factor is its polysaccharide capsule which interferes with complement-mediated phagocytosis. C. neoformans infections ensue following inhalation of small desiccated less encapsulated propagules leading to pulmonary pneumonia or colonization of the hosts respiratory tract. Numerous murine experimental studies have shown major discrepancies in cryptococcal cell and capsule enlargement between the lung and brain. In this report, we describe a nonmurine experimental model of the striking variability between cryptococcal cell and capsule size diameters in histology sections of postmortem lung and brain in a fatal cryptococcal infection in a heart transplant recipient.