Histochemical evidence for phosphorylase, branching enzyme and glycogen synthetase activities in rat brain

Localization of glycogen synthase activity in liver of fasted normal and adrenalectomized rats after injection of dexamethasone

Hepatic glycogen synthase activity was localized in normal and adrenalectomized (ADX) rats after fasting overnight and in fasted ADX rats after injection of dexamethasone (DEX) 2-8 h prior to sacrifice to stimulate glycogen synthesis. Cryostat sections were incubated in medium containing substrate to demonstrate glycogen synthase activity as indicated by glycogen synthesized during incubation. Sections from fasted normal rats showed limited dispersed glycogen synthase activity in both periportal and centrilobular regions. In contrast, activity for glycogen synthase in hepatocytes from fasted ADX rats appeared as large aggregates in random hepatocytes throughout the lobule. Two hours after injection of DEX the reaction product appeared as aggregates in some hepatocytes, but other cells revealed dispersed enzyme activity. Glycogen synthase activity was evident in more hepatocytes after 4 h treatment with DEX and after 8 h virtually all hepatocytes contained abundant reaction product. The results suggest that synthase activity becomes concentrated in limited regions of selected hepatocytes in fasted ADX rats. DEX stimulation of glycogen synthesis for 4-8 h results in increased enzyme activity.

Brain isozyme of glycogen phosphorylase: immunohistological localization within the central nervous system

An antibody specific for the predicted carboxyterminal sequence of the human brain isozyme of glycogen phosphorylase (alpha-1,4-D-glucan:orthophosphate D-glucosyltransferase, EC 2.4.1.1) was generated to verify the carboxyterminal amino acid sequence of this protein. The isozyme-specific antibody was used to examine the localization of this protein in primate and non-primate brain. The highest levels of the brain isozyme in cerebrum and cerebellum were found in fibrous astrocytes, many with glial processes that appear to terminate upon blood vessels.

Human brain-type glycogen phosphorylase: quantitative localization in human tissues determined with an immunoassay system

Glycogen phosphorylase (EC 2.4.1.1) from human brain tissue was purified to homogeneity. Antisera were developed in rabbits with purified phosphorylase as the immunogen. Antibodies were first affinity-purified with a column of brain phosphorylase-coupled Sepharose, and then the antibody fraction was adsorbed with a column of muscle phosphorylase-coupled Sepharose to remove antibodies reactive also with muscle phosphorylase. By using the specific antibodies, a sandwich-type immunoassay system for measurement of brain phosphorylase was prepared. The assay system consisted of polystyrene balls with immobilized antibrain phosphorylase F(ab')2 fragments and the same antibody Fab' fragments labeled with beta-D-galactosidase from Escherichia coli. The assay was sensitive and specific to the brain phosphorylase. The minimum detection limit of the assay was 0.1 ng/assay tube, and the cross-reactivity of the assay with muscle phosphorylase was less than 1%. Tissue concentrations of immunoreactive brain-type phosphorylase were estimated. The phosphorylase was present in the heart at as high a level as in the brain. The immunoreactivity for brain phosphorylase was distributed widely at a significant concentration in various peripheral tissues, such as the digestive tract, bladder, aorta, liver, and testis. Immunohistochemical localization of brain phosphorylase in the CNS revealed that the enzyme is present in most astrocytes and amyloid bodies, as well as in some neurons in the cerebral cortex and Golgi cells in the cerebellar cortex.

Localization of glycogen synthase in brain

Antisera against glycogen synthase from canine brain were prepared and used for investigation of the localization of the enzyme in the brain. Antisera cross-reacted only with the 88-kilodalton protein that is the subunit of brain glycogen synthase. Immunoreactivity of glycogen synthase was universally distributed in all regions of the brain, although hippocampus, cerebral cortex, caudatoputamen, and cerebellar cortex had relatively high immunoreactivity. Light microscopic examination revealed that the immunoreactivity was found in all cell types, such as neurons in several regions, astrocytes, ependymal cells surrounding the ventricle, oligodendrocytes, and epithelial cells of the choroid plexus in the ventricle. Immunoreactive intensity was more prominent in neurons than glial cells. Immunostaining may be a useful tool for investigation of the state of glycogen metabolism under normal and pathological conditions.

Glycogen phosphorylase activity in the olfactory bulb of the young rat

The activity of glycogen phosphorylase, the enzyme that controls glycogen breakdown, was histochemically mapped in the olfactory bulbs of 19-day-old rats. The effect of early odor experience on subsequent olfactory bulb phosphorylase activity was also examined. The highest level of phosphorylase staining in the bulb (and seemingly the highest in the brain) was in the glomerular layer, followed by the external plexiform, internal plexiform, granule cell, and olfactory nerve layers. Virtually no activity was visible in the large output neurons of the bulb, mitral, and tufted cells. Early peppermint odor experience, previously shown to increase metabolic activity in specific glomerular foci as measured by 2-deoxyglucose uptake, had no apparent effect on glomerular-layer phosphorylase activity. In some odor-familiar animals, however, patches of activity were seen in the internal plexiform layer in the area of the bulb where foci of high deoxyglucose uptake are seen in response to peppermint. The patches were directly in line with modified glomerular clusters often seen to underlie foci of enhanced deoxyglucose uptake. The existence of particularly heavy activity in the peripheral third of the glomerular layer, where glycogen-containing modified Schwann cells have been localized, raises the possibility that the glomerular-layer activity is at least partially glial in origin. Finally, because of its rich noradrenaline and serotonin innervation and high density of insulin receptors, the olfactory bulb is proposed as a model system to study the interaction of glycogen/glucose metabolism with neural activity in a relatively well-defined neuronal circuit.

Spatial relationship of histochemically demonstrable patches in the mouse superior colliculus

Patches of high phosphorylase activity are found in the intermediate and dorsal deep grey layers of the mouse superior colliculus when either coronal or sagittal sections are cut. These patches indicate that the phosphorylase a activity is arranged in a continuous lattice composed of bands of high phosphorylase a activity with a width of 100-200 microns that surround pale islands of low activity. This lattice was demonstrated by cutting surface parallel sections through the partially flattened superior colliculus. An almost identical lattice is observed in sections incubated to demonstrate total phosphorylase or cytochrome oxidase (CYO) activity. This phosphorylase/CYO lattice extends over the entire area of the superior colliculus. A discontinuous staining pattern is also observed in the intermediate and deep grey layers of both sagittal and coronal sections incubated for acetylcholinesterase (AChE) activity. The staining is arranged in two discontinuous sheets of intense activity that are joined together by vertical streamers. In surface parallel sections the AChE activity is found to form a network pattern which extends over the entire extent of the superior colliculus but which becomes fainter at the anterior pole. The phosphorylase/CYO lattice is not in register with the AChE lattice and the two seem to be organized independently of each other despite occurring at the same depth.

Axotomy increases glycogen phosphorylase activity in motoneurones

The relative distribution of glycogen phosphorylase a and b in the lumbar spinal cord of the adult rat following either transection or crush of the sciatic nerve has been studied. The activity of the glycogen phosphorylase was measured histochemically by its capacity to convert glucose-1-phosphate to glycogen which was then stained with iodine. Prior to any treatment, the enzyme was largely in its inactive b form. Sciatic section and crush produced a transient (24 h) decrease in the amount of the active glycogen phosphorylase a in the sciatic motoneurone pool. Fourteen days post-transection, but not crush, a marked increase in the level of the active glycogen phosphorylase a form of the enzyme could be detected in the axotomised motoneurones which persisted for up to 6 weeks. No equivalent changes occurred in the axotomized dorsal root ganglion cells. Glycogen phosphorylase although normally present in neurones in its inactive b form can be converted to the active a form by calcium or adenosine 3':5'-phosphate. The substantial increase in the level of glycogen phosphorylase a in axotomized motoneurones may be a reflection of an increased calcium influx into these cells due to the development of abnormally hyperexcitable membranes and the appearance of dendritic spikes that is known to occur in these motoneurones.

Organization of the mouse cerebral cortex: a histochemical study using glycogen phosphorylase

The postmortem phosphorylase a activity in cryostat sections taken from the brains of mice killed without any prior period of maintained anaesthesia ('unanaesthetized' mice) was compared histochemically with the activity in sections taken from mice anaesthetized with pentobarbitone prior to decapitation ('anaesthetized' mice). This study provides evidence for the existence of two separate overlapping modular subdivisions of the somatosensory cortex. The modules observed in the 'unanaesthetized' mice were restricted to layer IV and corresponded to the hollows of the whisker barrels where the thalamic afferents terminate. In contrast, the modules observed in the 'anaesthetized' mice extended from layer I to layer V, and formed a mosaic of cylinders that was out of register with the whisker barrels. These cylinders may correspond to the terminal fields of corticocortical afferents. In a few of the 'unanaesthetized' mice bands of high phosphorylase a activity are evident in the visual areas 17 and 18. This suggests that in the mouse, as in higher mammals, the thalamic input to the visual cortex gives rise to a columnar organization. In the 'anaesthetized' mice the mosaic of modules observed in the somatosensory cortex is also present in the auditory and motor areas. The modules in both groups of mice have similar diameters of between 200 and 350 microns.

An inverse relation between mitochondrial hexokinase content and phosphoglucomutase activity of rat tissues

The hexokinase: fumarase ratios of mitochondria isolated from ten tissues of the rat were determined, and compared with the tissue content of phosphoglucomutase and phosphorylase, taken as representatives of enzymes concerned with glycogen metabolism. A generally inverse relationship was found between the mitochondrial hexokinase: fumarase ratio and phosphoglucomutase levels. The cytochrome: fumarase ratios were relatively invariant in these same mitochondria. The results are interpreted as indicating a specialization of mitochondria, with increased amounts to hexokinase being associated with the mitochondria in tissues exhibiting less dependence on glycogen metabolism, as judged from phosphoglucomutase levels.