Immunocytochemical localization of glycogen phosphorylase in primary sensory ganglia of the peripheral nervous system of the rat

Brain isoform glycogen phosphorylase as a novel hepatic progenitor cell marker

An appropriate liver-specific progenitor cell marker is a stepping stone in liver regenerative medicine. Here, we report brain isoform glycogen phosphorylase (GPBB) as a novel liver progenitor cell marker. GPBB was identified in a protein complex precipitated by a monoclonal antibody Ligab generated from a rat liver progenitor cell line Lig-8. Immunoblotting results show that GPBB was expressed in two liver progenitor cell lines Lig-8 and WB-F344. The levels of GPBB expression decreased in the WB-F344 cells under sodium butyrate (SB)-induced cell differentiation, consistent with roles of GPBB as a liver progenitor cell marker. Short hairpin RNA (shRNA)-mediated GPBB knockdown followed by glucose deprivation test shows that GPBB aids in liver progenitor cell survival under low glucose conditions. Furthermore, shRNA-mediated GPBB knockdown followed by SB-induced cell differentiation shows that reducing GPBB expression delayed liver progenitor cell differentiation. We conclude that GPBB is a novel liver progenitor cell marker, which facilitates liver progenitor cell survival under low glucose conditions and cell differentiation.

Glycogen phosphorylase isozymes and energy metabolism in the rat peripheral nervous system--an immunocytochemical study

Glycogen represents the major brain energy reserve which is located mainly in astrocytes. Though the role of brain glycogen has drawn increasing attention, little is known about glycogen metabolism in the peripheral nervous system. In the present work, we have demonstrated immunocytochemically the ubiquitous presence of glycogen phosphorylase (GP), one of the major control sites in glycogen metabolism, in the axons of rat spinal and sciatic nerves, but not in Schwann cells. Application of isozyme-specific antibodies revealed the presence of the GP BB (brain) isoform, but not the MM (muscle) isoform. This is in accord with previous results demonstrating the presence of isoform BB, but not MM, in the few GP-containing brain and spinal cord neurons and in vagus nerve axons. In contrast, brain astrocytes express both isoforms. As GP BB is mainly regulated by the cellular AMP level, a special role of glycogen in the energization of the nerve axons is suggested. The cellular locations of hexokinase, pyruvate dehydrogenase and glucose transporters are discussed in respect to possible metabolic roles of glycogen in peripheral nerves.

Tracing the Neuroanatomical Profiles of Reward Pathways with Markers of Neuronal Activation

Functional neuroanatomical tools have played an important role in proposing which structures underlie brain stimulation reward circuitry. This review focuses on studies employing metabolic markers of neuronal and glial activation, including 2-deoxyglucose, cytochrome oxidase, and glycogen phosphorylase, and a marker of cellular activation, the immediate early gene c-fos. The principles underlying each method, their application to the study of brain stimulation reward, and their strengths and limitations are described. The usefulness of this strategy in identifying candidate structures, and the degree of overlap in the patterns of activation arising from different markers is addressed in detail. How these data have contributed to an understanding of the organization of reward circuitry and directed our thinking towards an alternative framework of neuronal arrangement is discussed in the final section.

Immunocytochemical localization of glycogen phosphorylase isozymes in rat nervous tissues by using isozyme-specific antibodies

Isozyme-specific antibodies were raised against peptides from the low-homology regions of the sequences of rat glycogen phosphorylase BB and MM isozymes by immunization of rabbits and guinea pigs. Immunocytochemical double-labelling experiments on frozen sections of rat nervous tissues were performed to investigate the isozyme localization pattern. Astrocytes throughout the brain and spinal cord expressed both isozymes in perfect co-localization. Ependymal cells only expressed the BB isozyme. Most neurones were not immunoreactive. The rare neurones that contained glycogen phosphorylase only expressed the BB isozyme. Nearly all of these neurones formed part of the afferent somatosensory system. These findings stress the general importance of glycogen in neural energy metabolism and indicate a special role for the glycogen phosphorylase BB isozyme in neurones in the somatosensory system.

Isozyme pattern of glycogen phosphorylase in the rat nervous system and rat astroglia-rich primary cultures: electrophoretic and polymerase chain reaction studies

Of the three isozymes of glycogen phosphorylase (GP) known, the brain (B) and muscle (M) isoforms have been reported to occur in brain. We investigated the regional and cellular occurrence of the three isozymes in various parts of the rat nervous system, fetal brain and astroglia-rich primary cultures by means of electrophoresis of native proteins with subsequent activity stain and by reverse transcriptase polymerase chain reaction. In the cortex, cerebellum, olfactory bulb, brainstem, spinal cord and dorsal root ganglia, both mRNA and enzyme protein were found for the B and M isozymes. In addition, the liver (L) isoform mRNA was detected in fetal brain and cultured astrocytes. Our studies indicate that there is no regional difference in distribution pattern between brain regions, spinal cord and dorsal root ganglia. In immature brain and cultured glial cells, the additional presence of the L isozyme is possible. These results support the idea that astrocytes express two or even three GP isozymes simultaneously.

Ultrastructural localization of glycogen phosphorylase predominantly in astrocytes of the gerbil brain

The localization of glycogen phosphorylase in gerbil brain was determined by immunoelectron microscopy using the pre-embedding peroxidase technique. Electron-dense granular reaction product of peroxidase activity was observed in astrocytes of all brain regions examined (cerebral cortex, striatum, cerebellar cortex, hippocampal formation, corpus callosum, mesencephalic trigeminal nucleus). The reaction product was distributed in a diffuse pattern throughout the cytoplasmic matrix of perikarya and processes; sometimes the nucleus of labeled astrocytes also contains immunopositive material. The light microscopically visible glycogen phosphorylase immunoreactivity associated with capillaries could be characterized as a staining of astrocytic endfeet ensheathing capillaries. Endothelial cells and pericytes were never labeled. In addition to astrocytes, ependymal cells also presented immunopositive material in their cytoplasm. On the other hand, no reaction product was observed in cells identified as oligodendroglia or microglia. Neurons (with the exception of neurons of the mesencephalic trigeminal nucleus), their processes, and their synaptic endings were free of reaction product. In the neuropil we frequently observed immunopositive glial processes adjacent to synaptic structures. This intimate spatial relationship may be interpreted as a morphological sign of a metabolic interaction. The data support the hypothesis that astroglia play a key role in glycogen metabolism and energization of the brain.