Faculty Opinions recommendation of Posttranslational modification of pili upon cell contact triggers N. meningitidis dissemination.

Thrombocytes (TC), the avian equivalent of blood platelets, support hemostasis by aggregating at sites of injury. Studies in our lab suggested that fibrinogen (fib) is a requisite cofactor for TC aggregation but operates by an undefined mechanism. To study the interaction of fib with TC and to identify fib receptors on cells, fib was purified from pigeon plasma, conjugated to colloidal gold and used both to facilitate aggregation and as a receptor probe. Described is the application of computer assisted reconstruction and stereo whole mount microscopy to visualize the 3-D organization of fib receptors at sites of cell contact in TC aggregates and on adherent cells.Pigeon TC were obtained from citrated whole blood by differential centrifugation, washed with Ca++ free Hank's balanced salts containing 0.3% EDTA (pH 6.5) and resuspended in Ca++ free Hank's. Pigeon fib was isolated by precipitation with PEG-1000 and the purity assessed by SDS-PAGE. Fib was conjugated to 25nm colloidal gold by vortexing and the conjugates used as the ligand to identify fib receptors.

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Neurofilaments and Paired Helical Filaments

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100120357 ◽

1985 ◽

Vol 43 ◽

pp. 740-743

Author(s):

J. Metuzals

Keyword(s):

Animal Model ◽

Posttranslational Modifications ◽

Posttranslational Modification ◽

Giant Axon ◽

Paired Helical Filaments ◽

Squid Giant Axon ◽

In Vitro Experiments ◽

Thin Sections ◽

Structural Relationships

It has been demonstrated that the neurofibrillary tangles in biopsies of Alzheimer patients, composed of typical paired helical filaments (PHF), consist also of typical neurofilaments (NF) and 15nm wide filaments. Close structural relationships, and even continuity between NF and PHF, have been observed. In this paper, such relationships are investigated from the standpoint that the PHF are formed through posttranslational modifications of NF. To investigate the validity of the posttranslational modification hypothesis of PHF formation, we have identified in thin sections from frontal lobe biopsies of Alzheimer patients all existing conformations of NF and PHF and ordered these conformations in a hypothetical sequence. However, only experiments with animal model preparations will prove or disprove the validity of the interpretations of static structural observations made on patients. For this purpose, the results of in vitro experiments with the squid giant axon preparations are compared with those obtained from human patients. This approach is essential in discovering etiological factors of Alzheimer's disease and its early diagnosis.

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On the Mechanism by which Cell Contact Induces the Release Reaction of Blood Platelets; the Effect of Cationic Polymers

Thrombosis and Haemostasis ◽

10.1055/s-0038-1649347 ◽

1972 ◽

Vol 27 (01) ◽

pp. 121-133 ◽

Cited By ~ 14

Author(s):

P Massini ◽

E. F Lüscher

Keyword(s):

Human Blood ◽

Calcium Ions ◽

Blood Platelets ◽

Cell Contact ◽

Second Phase ◽

Cationic Polymers ◽

Release Reaction ◽

Per Se ◽

Human Blood Platelets

SummaryHuman blood platelets are aggregated by the basic polymers polylysine and DEAE- dextran. Under certain conditions a second phase of aggregation, concomitant with the release reaction, is elicited. The presence of ADP, calcium ions and a plasmatic cofactor within the primary aggregates are necessary for the induction of the release reaction. These experiments demonstrate that cell contact per se does not lead to a release reaction ; in order to become effective it must take place in the presence of ADP.

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