Cytochemical localization of glucose-6-phosphatase activity in the central nervous system of the rat

Stephens, H. Brodie; Sandborn, Edmund B.

doi:10.1016/0006-8993(76)90011-1

Cited by 49 publications

(20 citation statements)

References 29 publications

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“…In addition, synaptic vesicles at the frog neuromuscular junction were shown to posses calcium-binding sites [18]. The alternative possibility that the calcium-transporting synaptosomal vesicles originate from endoplasmic reticulum type membrane is, of course, not ruled out since the enzyme marker glucose-6-phosphatase for brain endoplasmic reticulum [19] is present in every synaptosomal vesicles preparation tested. Synaptosomal vesicles are not an artifact formed from submitochondrial particles due to exposure of the nerve endings to hypo-osmotic media since their calcium transport is insensitive to uncouplers of oxidative phosphorylation or added atractyloside.…”

Section: Discussionmentioning

confidence: 99%

Calcium transport in a vesicular membrane preparation from rat brain synaptosomes

Rahamimoff¹,

Abramovitz²

1978

FEBS Letters

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Section: Discussionmentioning

confidence: 99%

Calcium transport in a vesicular membrane preparation from rat brain synaptosomes

Rahamimoff¹,

Abramovitz²

1978

FEBS Letters

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“…Biochemical data (Anchors and Karnovsky, 1975;Anchors et al, 1977;Karnovsky et al, 1983) and enzyme cytochemistry Cataldo, 1983, 1984;Cataldo and Broadwell, 1983) suggest that cerebral G6Pase functions predominantly as a phosphohydrolase to convert glucose-6-phosphate to glucose. Our methodology for G6Pase cytochemistry provides a more reliable and consistent preservation of cell morphology and G6Pase activity as well as a more extensive and accurate localization of G6Pase activity ultrastructurally in neural tissue than reported by others (AI-A11 and Robinson, 1981;Stevens and Sandborn, 1976;Teichberg and Holtzman, 1973). Some glucose-6-phosphate serving as a substrate for G6Pase in vivo may be provided by the degradation of glycogen stores (glycogenolysis).…”

Section: Introductionmentioning

confidence: 86%

Cytochemical identification of cerebral glycogen and glucose‐6‐phosphatase activity under normal and experimental conditions: I. Neurons and glia

Cataldo

Broadwell

1986

J. Elec. Microsc. Tech.

170

127

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Reliable ultrastructural techniques are applied for cytochemical identification of glycogen and localization of glucose-6-phosphate (GGPase) activity within neurons and glia of the adult mammalian CNS. Modulations in the cerebral localizations of glycogen and GGPase activity are identified during various experimental conditions (i.e., salt-stress, fasting, and trauma). The cytochemical reaction for demonstration of G6Pase activity implies that the enzyme acts as a phosphohydrolase to convert glucose-6-phosphate to glucose. The degradation of glycogen in vivo is one source of glucose-6-phosphate as a substrate for G6Pase. Glycogen is preserved by perfusion-fixation of the brain with 2% glutaraldehyde-2% formaldehyde. Chopper sections of this material are postfixed in buffered 1% osmium tetroxide-1.5% potassium ferrocyanide, which serves as a contrast stain for glycogen, or in buffered 1% osmium tetroxide. Plastic-embedded ultrathin sections of CNS tissue postfixed in 1% osmium tetroxide are stained for glycogen with periodic acid-thiocarbohydrazide-silver protein. Intracellular glycogen appears as electron-dense isodiametric particles and, under normal and experimental conditions, is most abundant within astrocytes. Neuronal glycogen is sparse to negligible normally but appears increased within specific neuronal populations during stressful states.Optimal preservation of GGPase activity in the brain is obtained by brief perfusion-fixation with 2% glutaraldehyde. Tissue sections are incubated in a modified Leskes medium containing glucose-6-phosphate or mannose-6-phosphate as substrate and lead nitrate. Utilizing the Gomori lead capture technique, G6Pase reaction product is localized within the lumen of the endoplasmic reticulum (ER) and related organelles (Lea, nuclear envelope, Golgi complex) of perikarya, dendrites, and glia. The ER in axons and axon terminals fails to express G6Pase activity under normal conditions but does so in some neurons exhibiting a degenerating appearance. A transient, cytochemical decrease in G6Pase activity may occur within some perikarya during stressed conditions.The results indicate that within neurons and glia of the adult CNS cytochemical stains are well suited for ultrastructural identification of glycogen and localization of G6Pase activity. Modulations in glycogen particle concentration

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“…There have been repons of his tochemical localisation of glucose-6-phosphate hydroly sis to a variety of brain cell types including neurons, oligodendroglia, astrocytes and many other cells [27][28][29][30][31]. This sometimes confusing literature reflects limita tions of the conventional lead salt method of phosphate detection.…”

Section: Brain Glucose-6-phosphatasementioning

confidence: 99%

A Role for Astrocytes in Glucose Delivery to Neurons?

et al. 1996

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The present paper examines the possible role of astrocytes in the delivery of glycogen-derived glucose for neuronal metabolism. Such a process would require astrocytic expression of glucose-6-phosphatase. The degree and significance of brain expression of glucose-6-phosphatase (EC 3.1.3.9) has been a subject of controversy. Published immunohistochemical data are consistent with expression of glucose-6-phosphatase by astrocytes, both in vivo and in vitro. In this paper additional confirmation of the expression of glucose-6-phosphatase mRNA in rat brain is presented. Although cultured astrocytes demonstrate glucose-6-phosphatase activity in vitro under assay conditions, there is very limited in vitro evidence that this activity confers a glucose-export capacity on astrocytes. Under most conditions in vitro, lactate export predominates, however this may relate to aspects of the in vitro phenotype. Data relating to astrocytic glucose and lactate export are considered in the context of hypotheses of trafficking by astrocytes of substrates for neuronal metabolism, hypotheses that imply and require compartmentation of these substances, in contrast with current formulations of glucose transport into and within brain that imply no glucose compartmentation. Microdialysis studies of the properties of the brain extracellular fluid (ECF) glucose pool in the freely moving rat were performed seeking evidence of glucose compartmentation. Results of these studies do imply compartmentalisation of brain glucose, and are consistent with a model envisaging the majority of glucose reaching the neuron via the astrocytic intracellular space and the ECF. In addition, such studies provide evidence that rises in ECF glucose concentration are not the direct result of local recruitment of cerebral blood flow, but suggest the influence of intermediate, astrocyte-based mechanisms. Astrocytic glucose-6-phosphatase may permit astrocytes to modulate the transastrocytic flux of glucose to adjacent neurons in response to signals reflecting increased neuronal demand.

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Cytochemical localization of glucose-6-phosphatase activity in the central nervous system of the rat

Cited by 49 publications

References 29 publications

Calcium transport in a vesicular membrane preparation from rat brain synaptosomes

Calcium transport in a vesicular membrane preparation from rat brain synaptosomes

Cytochemical identification of cerebral glycogen and glucose‐6‐phosphatase activity under normal and experimental conditions: I. Neurons and glia

A Role for Astrocytes in Glucose Delivery to Neurons?

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