Labeling of hepatic glycogen after short‐ and long‐term stimulation of glycogen synthesis in rats injected with <sup>3</sup>H‐galactose

Michaels, John E.; Garfield, Sanford A.; Hung, Julia T.; Cardell, Robert R.

doi:10.1002/aja.1001880410

Cited by 3 publications

(1 citation statement)

References 25 publications

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“…When they have been activated, NK cells augment innate immune responses via cross-talk with other cell types. This positive role for NK cells in initiating immune responses is supported by findings that other bacterial toxins inhibit NK cells, including leukotoxin derived from Actinobacillus actinomycetemcomitans and exotoxin A from Pseudomonas aeruginosa (61,62). We also suggest a positive role for NK cells in alerting the immune system to infection, but our observation stands distinct from these prior studies in that we show that NK cells undergo pyroptosis.…”

Section: Discussionsupporting

confidence: 72%

Siglec-7 engagement by GBS β-protein suppresses pyroptotic cell death of natural killer cells

Fong

Tsai

Saha

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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Natural killer (NK) cells are innate immune lymphocytes that recognize and destroy abnormal host cells, such as tumor cells or those infected by viral pathogens. To safely accomplish these functions, NK cells display activating receptors that detect stress molecules or viral ligands displayed at the cell surface, balanced by inhibitory receptors that bind to self-molecules. To date, such activating and inhibitory receptors on NK cells are not known to recognize bacterial determinants. Moreover, NK cell responses to direct interactions with extracellular bacteria are poorly explored. In this study, we observed the human neonatal pathogen group B Streptococcus (GBS) can directly engage human NK cells. The interaction was mediated through the B6N segment of streptococcal β-protein, binding to the inhibitory receptor Siglec-7 via its amino-terminal V-set domain. Unlike classical Siglec binding, the interaction is also independent of its sialic acid recognition property. In contrast to WT GBS, mutants lacking β-protein induced efficient pyroptosis of NK cells through the NLRP3 inflammasome, with production and secretion of the proinflammatory cytokine IL-1β and dissemination of the cytotoxic molecule granzyme B. We postulate that GBS evolved β-protein engagement of inhibitory human Siglec-7 to suppress the pyroptotic response of NK cells and thereby block recruitment of a broader innate immune response, i.e., by “silencing the sentinel.”

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Section: Discussionsupporting

confidence: 72%

Siglec-7 engagement by GBS β-protein suppresses pyroptotic cell death of natural killer cells

Fong

Tsai

Saha

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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

Michaels

Cardell

1997

Anat. Rec.

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Background The intralobular distribution of activity of glycogen phosphorylase (GP), a key enzyme in the breakdown of glycogen, was evaluated to determine changes during early glycogen synthesis. Hepatic GP activity was localized in normal and adrenalectomized (ADX) rats after fasting overnight and in fasted ADX rats stimulated to synthesize glycogen by administration of dexamethasone (DEX) 2‐8 h prior to sacrifice. Methods: Cryostat sections were incubated in medium containing appropriate substrate for demonstration of GP activity as indicated by glycogen synthesized by the enzyme during incubation. Results: In sections from fasted normal rats, GP activity in hepatocytes varied from undetectable to substantial amounts with no notable periportal to pericentral gradient evident. In contrast, GP activity in sections from adrenalectomized fasted rats was concentrated in discrete aggregates in random hepatocytes throughout lobules. Two hours after DEX injection, GP enzyme activity occurred as single aggregates or in a dispersed pattern in many hepatocytes. By 4 h after DEX administration, most cells displayed GP enzyme activity, the concentration of which appeared to be greater in pericentral cells than in periportal cells. Eight hours after injection of DEX, GP enzyme activity had increased and appeared more evenly distributed throughout the lobules. Conclusions: These results suggest that GP activity became concentrated in limited regions of selected hepatocytes in fasted ADX rats. DEX stimulation of glycogen synthesis in these rats resulted in increased GP activity that was concentrated in pericentral cells after 4 h. After 8 h, activity increased and was more evenly distributed throughout the lobules. The increase in GP enzyme activity concurrent with overall glycogen synthesis suggests that the enzyme may participate in glycogen turnover. Anat. Rec. 248:406‐412, 1997. © 1997 Wiley‐Liss, Inc.

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The influence of buffers during fixation on the appearance of smooth endoplasmic reticulum and glycogen in hepatocytes of normal and glycogen-depleted rats

Kuhn

Wild

1992

Histochemistry

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Liver tissue of normal and glycogen depleted rats was prepared for transmission electron microscopy by perfusion fixation and subsequent osmication in the presence of various buffers, dehydration in aethanol and embedding in epon. The use of Na/K-phosphate or Na-cacodylate to buffer glutaraldehyde led to similar appearance and distribution of SER. When Na-cacodylate was used during osmication, more SER membranes were retained but less accumulations of glycogen were found than after osmication in the presence of Na/K-phosphate. Fixation with s-collidine buffered osmium led to an easily recognisable network of SER comprising wide tubules whereas glycogen was hindered to be stained. Veronal acetate or Na-cacodylate supplemented with sucrose resulted in marked dilation and disintegration of SER. A similar effect was obtained when Na/K-phosphate or Na-cacodylate was used in hyposmolar concentration as buffer for glutaraldehyde. Liver of fasted rats or glucagon-treated rats after perfusion with Na/K-phosphate buffered glutaraldehyde and osmication in the presence of Na/K-phosphate or Na-cacodylate comprised glycogen-depleted hepatocytes which contained abundant SER membranes occupying the entire space between other organelles even in samples harvested 3 h after glucagon administration. The diversity in appearance and distribution of SER and glycogen granules, which depends to a large extend on the buffer used, suggests that SER membranes may not be sufficiently stabilized during aldehyde fixation and osmication. We thus consider it likely that large accumulations of glycogen granules are the consequence of disintegration of SER membranes during processing rather than they represent the morphologic substrate of physiological degradation of SER membranes in the course of glycogen synthesis and deposition.

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Labeling of hepatic glycogen after short‐ and long‐term stimulation of glycogen synthesis in rats injected with ³H‐galactose

Cited by 3 publications

References 25 publications

Siglec-7 engagement by GBS β-protein suppresses pyroptotic cell death of natural killer cells

Siglec-7 engagement by GBS β-protein suppresses pyroptotic cell death of natural killer cells

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

The influence of buffers during fixation on the appearance of smooth endoplasmic reticulum and glycogen in hepatocytes of normal and glycogen-depleted rats

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Labeling of hepatic glycogen after short‐ and long‐term stimulation of glycogen synthesis in rats injected with 3H‐galactose

Cited by 3 publications

References 25 publications

Siglec-7 engagement by GBS β-protein suppresses pyroptotic cell death of natural killer cells

Siglec-7 engagement by GBS β-protein suppresses pyroptotic cell death of natural killer cells

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

The influence of buffers during fixation on the appearance of smooth endoplasmic reticulum and glycogen in hepatocytes of normal and glycogen-depleted rats

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Labeling of hepatic glycogen after short‐ and long‐term stimulation of glycogen synthesis in rats injected with ³H‐galactose