Transmission Electron Microscopy: A Surgical Pathology Tool for Neuroblastoma.

Pediatric small round blue cell tumors (PSRBCT) are an intriguing and challenging collection of neoplasms. Light microscopy of small round blue cell tumors identifies small round cells. They harbor a generally hyperchromatic nucleus and relatively scanty basophilic cytoplasm. Pediatric small round blue cell tumors include several entities. Usually, they incorporate Wilms tumor, neuroblastoma, rhabdomyosarcoma, Ewing sarcoma, retinoblastoma, lymphoma, and small cell osteosarcoma, among others. Even using immunohistochemistry, the differential diagnosis of these neoplasms may be controversial at light microscopy. A faint staining or an ambiguous background can deter pathologists from making the proper diagnostic decision. In addition, molecular biology may provide an overwhelming amount of data challenging to distinguish them, and some translocations may be seen in more than one category. Thus, transmission electron microscopy (TEM) can be extremely valuable. Here we emphasize the modern protocol for TEM data of the neuroblastoma. Tumor cells with tangles of cytoplasmic processes containing neurosecretory granules can diagnose neuroblastoma.

Yunis-Varón syndrome caused by biallelic VAC14 mutations.

Yunis-Varón syndrome (YVS) is an autosomal recessive disorder comprising skeletal anomalies, dysmorphism, global developmental delay and intracytoplasmic vacuolation in brain and other tissues. All hitherto-reported pathogenic variants affect FIG4, a lipid phosphatase involved in phosphatidylinositol (3,5)-bisphosphate [PtdIns(3,5)P2] metabolism. FIG4 interacts with PIKfyve, a lipid kinase, via the adapter protein VAC14; all subunits of the resulting complex are essential for PtdIns(3,5)P2 synthesis in the endolysosomal membrane compartment. Here, we present the case of a female neonate with clinical features of YVS and normal FIG4 sequencing; exome sequencing identified biallelic rare coding variants in VAC14. Cultured patient fibroblasts exhibited a YVS-like vacuolation phenotype ameliorated in a dose-dependent fashion by ML-SA1, a pharmacological activator of the lysosomal PtdIns(3,5)P2 effector TRPML1. The patient developed a diffuse leukoencephalopathy with loss of the normal N-acetylaspartate spectrographic peak and presence of a large abnormal peak consistent with myoinositol. We report that VAC14 is a second gene for Yunis-Varón syndrome.

Real-time measurement of free Ca2+ changes in CNS myelin by two-photon microscopy.

Here we describe a technique for measuring changes in Ca2+ in the cytosolic domain of mature compact myelin of live axons in the central nervous system (CNS). We label the myelin sheath of optic nerve and dorsal column axons by using the Ca2+ indicator X-rhod-1 coupled with DiOC6(3) to produce bright myelin counterstaining, thereby providing unambiguous identification of the myelin sheath for analysis of two-photon excited fluorescence. We present evidence for localization of the Ca2+ reporter to the cytosolic domain of myelin, obtained by using fluorescence lifetime, spectral measurements and Mn2+ quenching. Chemical ischemia increased myelinic X-rhod-1 fluorescence (approximately 50% after 30 min) in a manner dependent on extracellular Ca2+. Inhibiting Na+-dependent glutamate transporters (with TBOA) or glycine transporters (with sarcosine and ALX-1393) reduced the ischemia-induced increase in Ca2+. We show that myelinic N-methyl-D-aspartate (NMDA) receptors are activated by the two conventional coagonists glutamate and glycine, which are released by specific transporters under conditions of cellular Na+ loading and depolarization in injured white matter. This new technique facilitates detailed studies of living myelin, a vital component of the mammalian CNS.