Meningothelial rosettes in the canine subarachnoid space

Summary A previously unrecognized type of rosette consisting of meningothelial cells is reported. Meningothelial clusters with a formation of numerous rosettes were incidentally observed in the canine subarachnoid space after single subarachnoid, injection of 0.2 mg/kg of epinephrine. Light microscopy revealed that the cell clusters with distinct rosettes occurred in the extensive cords and nests, surrounding the small subarachnoid arteries or adhering to the arachnoid epithelium. There were scattered mast cells adjacent to the cell clusters. Electron microscopy revealed that the resettes usually consisted of four to 12 tightly packed cells which were arranged like spokes and contained concentrations of tonofilaments. The rosette cells were knitted together by numerous junctional devices, such as desmosomes and desmosome-like junctions as well as a small number of interdigitations at the lateral surfaces toward the central core. The latter measured approximately 0.77–12.72 m in long diameter, containing electrondense, coarsely granular material. Both intracytoplasmic and extracellular inclusions with projecting microvilli were reminiscent of hyaline inclusions in certain meningiomas.     

Immunohistochemical study of erythropoietin in cerebellar hemangioblastomas associated with secondary polycythemia

Although cerebellar hemangioblastomas are known to be associated with secondary polycythemia, the cellular derivation of erythropoietin (EPO) in hemangioblastomas still remains obscure. Specimens from 18 patients with cerebellar hemangioblastomas were immunohistochemically studied using anti-EPO monoclonal antibody. Eight cases of brain tumors, including 2 meningiomas, 2 medulloblastomas, 2 glioblastomas, and 2 metastatic brain tumors were studied as controls. In 9 of 18 cases, EPO-positive cells were scattered around the capillaries and were ultrastructurally shown to be mast cells. These cases were not, however, associated with secondary polycythemia. In contrast, the stromal cells were positive for EPO in 3 cases. Among them, one was associated with secondary polycythemia. Furthermore, one-half of the control cases of brain tumor contained EPO-positive mast cells. Accordingly, it was suggested that mast cells (or small granulocytes) have little relationship to the release of EPO; however, some stromal cells might release EPO with a resultant polycythemia.     

A putative link of PUFA, GPR40 and adult-born hippocampal neurons for memory

Long chain polyunsaturated fatty acids (PUFA) such as docosahexaenoic and arachidonic acids, which are enriched in the brain, are important for multiple aspects of neuronal development and function including neurite outgrowth, signal transduction and membrane fluidity. Recent studies show that PUFA are capable of improving hippocampal long-term potentiation, learning ability of aged rats, and cognitive function of humans with memory deficits, although the underlying mechanisms are unknown. There have been several reports studying physiological roles of G-protein coupled receptor 40 (GPR40) in the pancreas, but no studies have focused on the function of GPR40 in the brain. As GPR40 was recently identified in neurons throughout the brain, it is probable that certain PUFA may act, as endogenous ligands, on GPR40 at their cell surface. However, the effects of PUFA upon neuronal functions are still not clearly understood. Here, although circumferential, a combination of in vitro and in vivo data is introduced to consider the effects of docosahexaenoic and arachidonic acids on brain functions. GPR40 was found in the newborn neurons of the normal and postischemic hippocampi of adult macaque monkeys, while the positive effects of PUFA upon Ca(2+) mobilization and cognitive functions were demonstrated in both GPR40 gene-transfected PC12 cells and human subjects with memory deficits. The purpose of this review is to propose a putative link among PUFA, GPR40, and hippocampal newborn neurons by discussing whether PUFA can improve memory functions through GPR40 activation of adult-born neurons. At present, little is known about PUFA requirements that make possible neurogenesis in the adult hippocampus. However, the idea that 'PUFA-GPR40 interaction might be crucial for adult neurogenesis and/or memory' should be examined in detail using various experimental paradigms.     

MR of acoustic neuromas--relationship to cranial nerves

In this report, the relationship of acoustic neuromas to the adjacent cranial nerves is discussed. On T1-weighted images, the trigeminal nerve was detected in all 13 cases. Mild to marked compression of these nerves by the tumors was observed in eight cases. The extent of compression did not always correspond to the clinical symptoms. In four cases with a maximum tumor diameter of 2 cm or less, the 7th and 8th cranial nerves were identified. There was no facial palsy in these patients. Two patients with a tumor diameter of more than 2 cm also had no facial palsy. All patients, including those with small tumors, complained of hearing loss and/or tinnitus. While MR imaging has some limitations, it is an effective imaging modality for showing the relationship between tumors and nerves.     

Surgical procedure "simplified retrosigmoid approach" for C-P angle lesions.

Previously, we reported surgical results of the simplified retrosigmoid approach for vestibular nerve sectioning in the cases with intractable vertigo. Here, we introduce in details surgical procedures of the simplified retrosigmoid (also called "subasterional" here for simplification) approach developed by one of the authors (J.H.L.). This approach is to operate cerebello-pontine (C-P) angle lesions through a small upper lateral window below the transverse-sigmoid junction. The retroauricular 4-5 cm skin incision, triangular craniectomy 2 cm in width, dural opening and closure, special considerations, and reconstruction of the skull defect were outlined. The bony landmarks for triangle craniectomy below asterion were described in detail. The C-P angle was appropriately approached for microvascular decompression, removal of C-P angle tumors, and vestibular nerve resection. This subasterional approach was characterized by short operation time of 1-3 h and less postoperative discomforts compared to the conventional retrosigmoid approach.