Title page for ETD etd-12192011-100555


Document Type Master's Dissertation
Author Engelbrecht, Mia-Jeanne
Email engelbrecht.mia@gmail.com
URN etd-12192011-100555
Document Title Investigating the ultrastructure of fibrin networks, platelets and coagulation profiles in healthy individuals
Degree MSc
Department Anatomy
Supervisor
Advisor Name Title
Prof E Pretorius Supervisor
Keywords
  • healthy individuals
  • platelets
  • fibrin networks
  • coagulation profiles
Date 2011-09-09
Availability restricted
Abstract
Normal blood flow in healthy individuals is achieved by the maintenance of a balance between the procoagulant and anticoagulant (fibrinolytic) pathways in the blood. A number of changes occur during aging with regards to fibrin network structure, platelet morphology and the overall coagulation profile of individuals. The aim of this study was to determine the characteristics necessary for fibrin networks and platelets to be classified as healthy as well as the effect of aging and sex on the coagulation potential of healthy individuals.

36 Voluntary individuals (separated into six different age groups) were selected and their platelets, fibrin networks and coagulation potential were studied using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Fibrinogen Levels and Thromboelastography® (TEG®). For SEM and TEM thrombi were formed by the addition of human thrombin to the freshly prepared platelet-rich plasma of the participants. The thrombi were fixed and prepared according to electron microscopy guidelines before being viewed. Fibrinogen Levels and TEG® were performed by trained technicians in a Haematology Laboratory. Statistical analysis was performed on the fibrin fibres of the fibrin networks to determine the average diameter of the fibres and to compare the fibre thickness of different individuals in different age groups. Statistical analysis was also performed on the TEG® results in order to compare the TEG® variables of each age group.

With regards to the coagulation profiles of the participants the Fibrinogen Levels were found to increase with age, but was not statistically significant. The same was true for the TEG® variables, Alpha Angle and Maximum Amplitude. The Reaction Time and KTime, however, decreased with an advance in age, but not with statistical significance.

The TEG® Index however was found to increase with statistical significance with advancing age (P=0.0065). All the variables were found to be within the normal set medical ranges provided by the manufacturers. The ultrastructure of fibrin networks were found to consist mostly of major fibres with minor fibres sparsely arranged in between, especially in younger individuals. The fibrin networks become denser with an advance in age and seem to be due to an increase in the amount of minor fibres. Statistically the obtained histograms did not have the expected bimodal distribution pattern, but rather appeared “merged” with no clear distinction between the major and minor fibres. With advancing age the thin fibres form “net-like” structures that cover sections of the thrombus. Fibre bundles could be observed after the age of 50. Platelet surface morphology was found to be similar in all the age groups and the same was true for the platelet interior. The overall amount of granules within the granulomere of the platelets was found to decrease after the age of 40. Slight spreading of the platelets could be observed in ages over 50 years.

The TEG® Index was found to be directly proportional to an advance in age. The TEG® variables, however, did not differ significantly between the six assessed age groups. No statistically significant difference could be observed when comparing the Fibrinogen Levels of the participants. Changes in the fibrin network morphology, related to aging, systematically increase due to aging and are most prominent after the age of 60. Intermediate fibre diameters were found to be present in addition to the major and minor fibres. Major fibres appear to decrease in diameter with advancing age, rather than decreasing in number. Platelet morphology showed no real differences with an increase in age when comparing the different age groups. Sex-related differences could not be found with regard to platelet morphology and coagulation profiles; however, the fibrin network structure appears to be influenced by sex. Sex-related differences in the fibrin network morphology were found to appear after the age of 30 and persisted up to the age of 60 after which the differences seem to disappear. From the results obtained in the current study, it can therefore be concluded that age-related changes occur in all individuals, but are most prominent in the SEM images of the fibrin network ultrastructure. Sex-related differences could only be observed in fibrin networks. Electron microscopy can thus be assumed to be more sensitive to alterations in coagulation than blood assays such as TEG®.

© 2011, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Engelbrecht, MJ 2011, Investigating the ultrastructure of fibrin networks, platelets and coagulation profiles in healthy individuals, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-12192011-100555 / >

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