Wendy Jeannette Van der Spuy

Qualitative scanning electron microscopy analysis of fibrin networks and platelet abnormalities in diabetes.

Diabetes is a condition defined by hyperglycaemia and these patients have a high risk of thrombosis. Previous research showed that ultrastructural changes in clot formation occur in patients in whom there are changes in the coagulation system due to, for example, an inflammatory condition. In the current study, the ultrastructures of platelets and fibrin networks were investigated in 25 diabetic patients. Plasma smears, with and without the addition of thrombin, were prepared. Results indicated that the fibrin network in all diabetic patients had thickened masses of thin, minor fibres over the major fibres, a profile typical of an inflammatory condition. A changed platelet membrane ultrastructure could also be observed in the diabetic patients that revealed typical apoptotic morphology, in whom membrane blebbing could be seen. It can, therefore, be concluded that in diabetic patients, the ultrastructure of fibrin networks show a typical systemic inflammatory profile, although platelets seem to be apoptotic.

Interaction of Fibrin with Red Blood Cells: The Role of Iron

Activation of coagulation pathways results in the formation of hemostatic fibrin plugs. Under normal physiologic conditions fibrin clots are gradually, albeit completely, degraded by a fibrinolytic enzyme system to ensure proper wound healing and/or blood vessel patency. Yet in pathological situations, thrombi are not effectively removed, leading to chronic thrombosis. The susceptibility of blood clots to enzymatic degradation depends on the structure and properties of fibrin fibers. Many factors have been suspected as culprits, including red blood cells (RBCs) that become transiently trapped within fibrin mesh. Here, the authors show that there is indeed a specific interaction between RBCs and fibrin-like fibers identified here as dense matted deposits (DMDs) by means of scanning electron microscopy (SEM). It is emphasized that such interactions can be observed in ischemic stroke patients, but not from healthy subjects. However, DMD/RBC aggregates can be induced in normal blood by the additions of trivalent iron ions. The plausible mechanism of the enhanced fibrin–red blood cell interaction is based on the previously described iron-induced generation of hydroxyl radicals. These radicals cause, in turn, non-enzymatic formation of fibrinogen aggregates remarkably resistant to fibrinolysis that are also similar to DMDs described in this paper. In conclusion, this relatively simple SEM analysis may become a convenient tool for diagnosing prothrombotic conditions associated with iron overload. It is suggested that future research on prevention and treatment of ischemic stroke and other thrombosis associated diseases should include testing of iron-chelating and hydroxyl radical-scavenging agents.

Smoking and coagulation: the sticky fibrin phenomenon.

Smoking impacts on hemostasis and coagulation physiology is affected. Although this is well known, no previous research is available on the impact of smoking on fibrin network morphology. Here the authors show that smoking causes the fibrin network to have a netlike appearance in some areas, as well as areas where thick plaques are present. They argue that even in occasional smokers, fibrin, in the presence of thrombin, forms thickened areas that might be the cause of a thrombotic event such as stroke. Furthermore, it seems as if smoking impacts immediately on the fibrin architecture, and this therefore does not happen only over an extended period of smoking exposure. This information is important, particularly for women with additional risk during contraceptive use and pregnancy. The authors propose the term sticky fibrin phenomenon and suggest that this is the cause for thrombotic events during smoking.

A descriptive investigation of the ultrastructure of fibrin networks in thrombo-embolic ischemic stroke

Stroke is one of the leading causes of death worldwide. Formation of a fibrin clot is controlled by a group of tightly regulated plasma proteases and cofactors and a change in the fibrin fiber formation causes an alteration in clot morphology. This plays an important role during thrombotic events. In the current study we investigated the ultrastructure of fibrin networks from fifteen ischemic stroke patients by using scanning electron microscopy. Clot morphology was investigated with and without the addition of human thrombin to the platelet rich plasma. Previously it was shown that, when studying the ultrastructure of fibrin networks, the addition of thrombin is necessary to form an expansive, fully coagulated layer of fibers. Results from the addition of thrombin to the plasma showed thick, matted fibrin fibers and a net covering some of the major fibers in stroke patients. Typical control morphology with major thick fibers and minor thin fibers could be seen in some areas in the stroke patients. In stroke patients, without the addition of thrombin, a matted fibrin network still formed, indicating that the factors responsible for the abnormal fibrin morphology are present in the circulating plasma and is the cause of the observed matted, layered morphology. This is not present in healthy individuals. From the results obtained we suggest that this changed morphology might be useful in a screening regime to identify the possibility of a stroke or even to follow the progress of stroke patients after treatment.

Interrelation between inflammation, thrombosis, and neuroprotection in cerebral ischemia

Abstract Stroke by mechanism of thrombotic cerebral ischemia is one of the leading causes of death and/or disability worldwide. Current research is under consensus that there are sex-based differences in both the prevalence and presentation of stroke and thrombosis. Here we discuss the interrelation between thrombosis and inflammation and call attention to points in the cerebral ischemic cascade where estrogen may be involved in neuroprotection. Cerebral ischemia triggers a series of events including inflammation, which is deeply interrelated with thrombosis; inflammation not only produces local thrombosis, but thrombosis can also amplify inflammation especially through the synergism of leukocyte and platelet activity. Research involving experimental animal models of cerebral ischemia has shown that sex hormones, especially estrogen, offer a degree of neuroprotection. Mechanisms of this neuroprotection may be linked to certain anti-inflammatory properties of estrogen, as well as estrogen’s regulation of thrombosis through the lowering of coagulation factors, among others. It is also understood that sex hormones alter the function and morphology of platelets and fibrin networks, and changes in platelet and fibrin network morphology offer one of the earliest confirmations of inflammation. Sex hormone levels, inflammatory processes, and thrombotic mechanisms are profoundly interconnected in predicting the outcome of cerebral ischemia.

Scanning electron microscopy of fibrin networks in rheumatoid arthritis: a qualitative analysis

Rheumatoid arthritis is a chronic inflammatory condition that affects mainly synovial joints and has an impact on approximately 1% of the Western population. The coagulation process is altered in this condition, and this is frequently complicated by thrombocytosis. Changes in fibrin morphology have been linked with inflammation, and this, in turn, plays an important role in thrombosis. Changes in the fibrin fiber formation cause the alterations observed in thrombus morphology. In the current study, the ultrastructure of platelets and fibrin networks was investigated to determine whether any morphological changes are present in these structures in patients suffering from rheumatoid arthritis. Six patients diagnosed with rheumatoid arthritis took part in this study, and their clot morphology was compared to that of control subjects. Citrated blood with and without the addition of thrombin was used. Results indicated that the fibrin networks in the arthritis patients formed thick, matted layers. This matted appearance is due to a changed ultrastructure of the minor, thin fibers. Also, in these patients, spontaneous networks were created without the addition of thrombin, which indicates an abnormal hemostatic protein functioning, and the latter is expressed as visible changes in ultrastructure.

Is the use of resveratrol in the treatment and prevention of obesity premature

Obesity is a multi-faceted disease, predisposing sufferers to numerous co-morbidities such as epithelial dysfunction and insulin resistance which ultimately result in CVD. Visceral adipose tissue in particular is associated with inflammation due to the release of pro-inflammatory cytokines by adipocytes. Inflammation seems to be rather central in causing damage to endothelial cells as well as exerting negative effects on glucose metabolism, ultimately leading to insulin resistance. Resveratrol is a naturally occurring phenolic substance which has been found to display anti-inflammatory, vasoprotective and insulin-sensitising effects, among others. The popularity of resveratrol use is escalating in the treatment of various ailments including obesity in adults. The use of the substance in childhood obesity is, however, a worrying factor, as no studies have as yet been performed on adolescent animals and there is evidence of kidney toxicity of resveratrol and its metabolites at intake levels below those currently approved as safe. Another cause for concern is the uncertainty surrounding long-term, low-dose administration of the substance in humans. The supplement should thus not be recommended for use in the prevention and treatment of obesity until conclusive research is established on the safety of long-term usage of resveratrol in both children and adults.

The changed ultrastructure of fibrin networks during use of oral contraception and hormone replacement

Contraceptives and hormone replacement have been extensively used since the late 1950s. However, adverse effects are common and include an increased risk of cardiovascular diseases, including thrombo-embolic diseases. Previous research has shown that ultrastructure of fibrin networks may provide great insight regarding the thrombotic potential of patients. The current study investigates the scanning electron microscopy (SEM) ultrastructure of fibrin networks of individuals using oral contraceptive therapy as well as individuals using hormone replacement. We compare micrographs of these two groups with micrographs of young, healthy individuals not using oral contraception. Platelet rich plasma and thrombin was used to prepare the fibrin clots. Here we show that during contraceptive and hormone replacement use, a netted fibrin layer forms. We suggest that oestradiol use causes fibrin network changes and these changes can be seen using SEM technology. These changes may provide further evidence regarding the increased occurrence of thrombotic events during contraceptive and hormone replacement therapy.

Scanning electron microscopy investigation of fibrin networks after thermal injury.

Injury due to burning is known to impact on coagulation and haemostasis by disturbing the coagulation cascade and is also associated with impaired fibrinolysis. Also, venous thrombosis, pulmonary embolism and hypercoagulability are common during thermal injury. Using a Wistar albino rat model, we investigated in this study whether burn injury affects the ultrastructure of the fibrin networks. A typical fibrin network will contain mostly major, thick fibres with minor, thin fibres distributed amongst them. We found that the clot architecture changes after burn injury, showing more prominent minor, thin fibres in a netted appearance. Also, the clot showed areas of matted fibrin. We suggest that the thrombotic events associated with burn injury are due to the thickened and netlike areas formed when thrombin activates the coagulation cascade. This is due to impaired fibrinolysis activities, causing the resulting fibrin clots not to be successfully disseminated. Small fragments of these netted, clumped areas may therefore break loose and lead to thrombotic events after burn injuries. The current study therefore provided morphological evidence for thrombotic events associated with burn injury.

Ultrastructural Analyses of Platelets and Fibrin Networks in BALB/c Mice after Inhalation of Spherical and Rod-Shaped Titanium Nanoparticles

We wish to acknowledge the CSIR and Department of Anatomy, University of Pretoria who funded the laboratory and animal study.