scholarly journals CYTOCHEMISTRY OF 5-HYDROXYTRYPTAMINE AT THE ELECTRON MICROSCOPE LEVEL I. STUDY OF THE SPECIFICITY OF THE REACTION IN ISOLATED BLOOD PLATELETS

1968 ◽  
Vol 16 (3) ◽  
pp. 162-171 ◽  
Author(s):  
GUILLERMO JAIM ETCHEVERRY ◽  
LUIS MARIA ZIEHER
Keyword(s):  
Electron Microscope ◽  
Blood Platelets ◽  
Microscope Level ◽  
Storage Site ◽  
Electron Microscope Level ◽  
Dense Granules ◽  
Amine Content ◽  
Level I ◽  
Previous Assumption

Blood platelets obtained from normal rabbits and those isolated from reserpine-treated animals and subsequently incubated in vitro with 5-hydroxytryptamine, norepinephrine and histamine were assayed for amine content or processed for examination under the electron microscope. With the glutaraldehyde-dichromate reaction for unsubstituted catechol- and indoleamines, reactive granules were observed in normal platelets. Formaldehyde fixation prior to the glutaraldehyde-dichromate reaction resulted in a similar image under the electron microscope. In platelets obtained from animals treated with reserpine a decrease of the amine content with a corresponding reduction in the number of dense granules was observed. Following incubation with 5-hydroxytryptamine the concentration of the amine increased markedly and the number of dense granules that reacted with both techniques became practically normal. In norepinephrine-incubated platelets dense granules were demonstrated with the glutaraldehyde-dichromate reaction, but no reactive products were observed using prefixation with formaldehyde. Histamine was also incorporated into depleted platelets but gave no reaction. It is concluded that prefixation with formaldehyde renders negative the reaction with catecholamines, leaving unaffected indoleamine-reactive sites. The previous assumption that the dense granules contain 5-hydroxytryptamine has been confirmed by such a cytochemical approach. The possibility that these organelles constitute a common storage site for different amines is discussed.

Synthesis and Localization of Sulphated Mucopolysaccharide in Megakaryocytes and Platelets of the Rat, An Analysis by Electron-Microscope Autoradiography

1972 ◽  
Vol 10 (3) ◽  
pp. 705-717
Author(s):  
G. G. MacPHERSON
Keyword(s):  
Electron Microscope ◽  
Golgi Apparatus ◽  
Blood Platelets ◽  
Total Activity ◽  
Electron Microscope Autoradiography ◽  
Dense Granules ◽  
Level Of Activity ◽  
Microscope Autoradiography ◽  
Almost All

Electron-microscope autoradiography has been used to investigate the synthesis and localization of sulphated mucopolysaccharide in megakaryocytes and blood platelets. Following 10-min incubation of bone marrow with 35S-sulpahte in vitro the majority of the activity in megakaryocytes was associated with the Golgi apparatus, but a substantial proportion was associated with other cytoplasmic organelles, suggesting either rapid transport or sulphation of mucopolysaccharide outside the Golgi apparatus. Three hours after the intravenous injection of 35SO4 only a small proportion of the total activity was associated with the Golgi apparatus, most being associated with demarcation membranes and dense granules, while 12 h after injection almost all the activity was associated with demarcation membranes and granules. A rising proportion of activity localized solely on the demarcation membranes suggested that they may possess some activity of their own. Autoradiographs of blood platelets prepared 72 h after the injection of 35SO4 were analysed. It was shown that most of the activity was associated with the α-granules, but there was strong evidence that the platelet membrane possessed a low level of activity.

Sequential Changes Associated with Cell Wall Formation and Fusion in the Vascular Cambium

IAWA Journal ◽  
1981 ◽  
Vol 2 (4) ◽  
pp. 151-162 ◽  
Author(s):  
A.M. Catesson ◽  
J.C. Roland
Keyword(s):  
Cell Wall ◽  
Electron Microscope ◽  
Cell Walls ◽  
Microscope Level ◽  
Cell Wall Formation ◽  
Characteristic Sequence ◽  
Electron Microscope Level ◽  
Starting Point ◽  
Cell Wall Development ◽  
Cambial Zone

Cytochemical techniques and mild extractions were used at the electron microscope level for the study of the cambial zone of several hardwoods and one softwood. The maturation processes of the primary radial and tangential cell walls involve a progressive disappearance of their initial heterogeneity. The buttress-like zone joining these walls appears to be the starting point for a characteristic sequence of changes and intra-wall rearrangement. Topochemical results have suggested an alternative to the 'emboxing concept' of cell wall development.

scholarly journals M6PR-Specific Targeting of Lysosomal Heparanase Regulates Platelet Hemostatic Function in Mice

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1059-1059
Author(s):  
Nathan Eaton ◽  
Caleb Drew ◽  
Theresa A. Dlugi ◽  
Karin M. Hoffmeister ◽  
Hervé Falet
Keyword(s):  
Platelet Function ◽  
Conflicts Of Interest ◽  
Blood Platelets ◽  
Critical Role ◽  
Fluorescent Microscopy ◽  
Type I ◽  
Dense Granules ◽  
Specific Targeting

Besides α-granules and dense granules, which play critical roles in and beyond hemostasis, circulating blood platelets and their precursor cells megakaryocytes contain lysosomes, the contents of which are also secreted during platelet activation. In their delivery to the lysosome, acid hydrolases bearing phosphomannosyl residues are trafficked from the trans-Golgi network to the acidic late-endosomal compartment via the mannose 6-phosphate receptor (M6PR) pathway. To determine the role of M6PR-specific targeting of lysosomal enzymes in platelet function, platelet parameters were investigated in M6pr-/- mice lacking the 46-kDa M6PR, the physiological role of which is unclear. M6pr-/- mice had normal platelet count but displayed an increased number of distinct proplatelet-like cells compared to control mice, as determined by immunofluorescent microscopy. Moreover, transmission electron microscopy revealed the presence of abnormal membrane tubulations, elongated and electron-dense granules, and large vacuole-like structures within resting M6pr-/- platelets. M6pr-/- platelets expressed normally major glycoproteins on their surface and von Willebrand factor and fibrinogen in their α-granules. M6pr-/- mice were hyper-thrombotic, as assessed by tail bleeding time, and M6pr-/- platelets adhered to type I collagen with a significantly greater propensity than control platelets under arterial shear in in vitro flow experiments. Heparanase, an endo-β-glucuronidase that cleaves extracellular matrix heparan sulfate proteoglycans, is the most abundant lysosomal enzyme in platelets. Thus, its contribution to the phenotype of M6pr-/- mice was investigated further. Heparanase expression was decreased in the bone marrow megakaryocytes and blood platelets of M6pr-/- mice and increased in M6pr-/- plasma, as evidenced by immunoblot and fluorescent microscopy analysis, consistent with its mistargeting in the absence of M6PR. Interestingly, pharmacological inhibition of heparanase with OGT 2115 normalized the adhesion of M6pr-/- platelets to collagen in vitro, indicating that increased plasma heparanase contributes to the thrombotic phenotype of M6pr-/- mice. Taken together, the data suggest that the M6PR-specific targeting of lysosomal heparanase plays a critical role in platelet function, thereby regulating hemostasis. Disclosures No relevant conflicts of interest to declare.

Infundibulomyces: a new genus of coelomycetes from Thailand

2003 ◽  
Vol 81 (7) ◽  
pp. 732-737 ◽  
Author(s):  
Narumol Plaingam ◽  
Sayanh Somrithipol ◽  
E B. Gareth Jones
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Light Microscope ◽  
Type Species ◽  
New Genus ◽  
Anamorphic Fungi ◽  
Microscope Level ◽  
Electron Microscope Level ◽  
Fallen Leaves ◽  
Scanning Electron

The genus Infundibulomyces is proposed for coelomycetous fungi with nidulariaceous-like conidiomata and bipolar appendaged conidia. Infundibulomyces cupulata sp. nov., collected from fallen leaves of Lagerstroemia sp. from Thailand, is described as the type species of the genus. This fungus is illustrated at the light microscope and scanning electron microscope level and compared with other morphologically related taxa. Cupulate conidiomata are uncommon and Infundibulomyces is compared with these.Key words: anamorphic fungi, coelomycete, Infundibulomyces, Thailand, tropical.

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