1,720,994 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Investigating lipopolysaccharide-induced inflammation in Sprague-Dawley rats on liver function with specific focus on coagulation factor production
Full text linkDissertation (MSc (Human Physiology))--University of Pretoria, 2023.Neurodegenerative diseases, such as Parkinson’s disease (PD) and Alzheimer’s disease (AD), have long confounded the scientific and medical communities. The extensive research into these diseases, particularly AD has produced several plausible theories on its progression, but this research has so far failed to yield any lasting results in producing an effective treatment of AD. With the increase of the prevalence of AD in an increasingly aging world population, elucidating a model of disease progression that takes into account the neurodegenerative characteristics that are hallmarks of the disease, along with its related metabolic and organ system effects has become a public health priority. Systemic inflammation has become one of the main components of several non-communicable diseases, in particular AD.
In this study, the aim was to investigate an emerging theory of AD pathogenesis that may combine the neurological and metabolic aspects that are often seen in these patients, the gut-liver axis theory. This theory states that the liver is the first organ to come into contact with circulating lipopolysaccharide (LPS), which would cause the kind of low-grade and chronic inflammation that would cause significant long-term damage to the liver, thus resulting in the organ system failure secondary to AD. Therefore, a model of LPS-induced inflammation was studied in adult male Sprague-Dawley rats to determine the effect of the systemically -induced LPS inflammation on the liver with particular focus on coagulation factor production and the possible prevalence of liver damage and fibrosis.
The model was successfully created over a 10-day period, after which the animals were terminated, and the liver tissuetissues collected and processed for use in light-microscopy and transmission electron microscopy (TEM). The levels of coagulation factors, tissue factor (TF) and fibrinogen (FG), were also determined by use of ELISA assays. Behavioural testing was used as a means to confirm the presence of AD-like symptoms in the model induced by the LPS administration.
Due to the low concentration of LPS administered into the animals during the experimental period, the levels of tissue factor and fibrinogen were not significantly higher or changed when compared with the control group. Similarly, the morphological analysis of liver tissue showed that the administration of LPS as designed in this study did not significantly affect the liver tissue. At an organelle level, it was found that the LPS administration produced a mild to moderate negative effect on the liver, an indication of the initial stages of liver damage due to the exposure of LPS.
In conclusion, the administration of LPS in Sprague-Dawley rats as modelled in this study did not induce the systemic inflammation that would cause significant liver damage and subsequent fibrosis, only producing the initial stages liver damage seen at sub-microscopic level. This however shows that short-term exposure to low levels of LPS will induce changes on a cellular level and that long-term exposure could accumulate to complications that could lead to clinical presentation.
Key words: inflammation, lipopolysaccharide, liverPhysiologyMSc (Human Physiology)Unrestricte
The potential neuroprotective effect of Manuka Honey in Sprague-Dawley rats with Lipopolysaccharide induced neuronal injury
Full text linkDissertation (MSc (Human Physiology))--University of Pretoria, 2021.Alzheimer’s type dementia is the most common form of dementia and is a large contributor to mortality in the aging and geriatric populations. It is associated with amyloid plaque formation, neurofibrillary tangles, neuro-inflammation and memory loss. There appears to be a causal link between the neuro-inflammation and other pathological processes associated with the development of Alzheimer’s type dementia and gastrointestinal presence of lipopolysaccharide (LPS), a component of the outer cellular membrane of Gram-negative bacteria. In addition to this, there is sufficient evidence suggesting honey as a possible treatment or preventative measure against inflammation and, therefore, against the neuro-inflammation associated with LPS and Alzheimer’s type dementia.
In the current study, LPS derived from Escherichia coli (E. coli) was chosen based on the increased prevalence of E. coli infections in South Africa, and Manuka honey was chosen as a treatment against LPS due to its proven therapeutic use and wide use in scientific study. Thus, the aim of this study was to investigate the possible effects of systemic LPS administration on the behaviour and the hippocampal region of the brain as well as investigate the possible protective effect of Manuka honey in a Sprague-Dawley model.
This model was successfully implemented using a sample size of 40 over a thirteen-day period after which the animals were terminated, perfused and the intact brain removed and processed for light- and transmission electron microscopy. In addition to this, antemortem studies were conducted to assess the overall health status and possible memory decline of the test subjects.
The daily LPS administration of 0.01 mg per kilogram animal weight resulted in no significant weight loss or gain among the animals. In addition to this, no sickness behaviour was observed throughout the thirteen-day period. The LPS administration had no significant effect on the brain to weight ratio or antemortem behavioural studies. Additionally, the daily exposure to 0.5 mL of honey per kilogram animal weight resulted in no significant weight changes or sickness related behaviours among the animals.
The morphology analysis of the hippocampal tissue demonstrated some altered metabolic activity and amyloid formation in the LPS exposed groups. The ultrastructural analysis indicated a decreased mitochondrial membrane integrity and enlarged rough endoplasmic reticulum in both exposed groups with these changes observed to a lesser extent in the honey exposed group.
In conclusion, this study suggests that LPS and honey exposure alone and in combination does produce some level of response in the dorsal hippocampal region of the Sprague Dawley rat brain. The response to LPS was not sufficient enough to produce statistically significant differences in behaviour amongst the groups; however, it was sufficient to produce differences in histological studies. This may be due to an insufficient exposure period or exposure concentration.PhysiologyMSc (Human Physiology)Unrestricte
The ex vivo effects of Naja mossambica venom on the ultrastructure and viscoelastic properties of human blood
Full text linkDissertaion (MSc )Human Physiology))--University of Pretoria, 2023.Snake bites are of a major global concern that may affect any individual in all age groups, gender, geographical location and economic status. Previous research has identified the effects of venomous snake bites of various species and families and the correlation with proteins found in snake venom. There is, however, limited research on the effects of the Naja mossambica (Mozambique spitting cobra) venom on the coagulation system, particularly the haematological system and blood rheology. In order to better understand the effects of Naja mossambica venom on the coagulation system, this research aimed to study the ex vivo physiological effects of Naja mossambica venom, of concentration 0.025 ng/μL, on human blood cells and the viscoelastic properties of the coagulation system. The methods used include light microscopy (LM) and scanning electron microscopy (SEM), which provided morphological data on red blood cells (RBCs), platelets, fibrin fibres and clot structure, particularly with the SEM. In addition,
Thromboelastography® (TEG®) was performed to study clot kinetics and clot formation and the Global thrombosis test® (GTT®) was performed to study platelet activity in relation to thrombin generation and thrombolysis. From the results, it was established that there was an increase in deformed RBCs, increased platelet activity, and fibrin fibres appeared loosely packed. Also, a
significant difference in the clot kinetics was noted, suggesting changed fibrin mechanics. Therefore, these results suggest hypo-coagulability in individuals exposed to Naja mossambica snake venom. The hypo-coagulable state in the victims might not be to an extent of bleeding events, however, this might have implications in blood flow and wound healing. This information can also be used in future studies to improve diagnostics or management strategies for snakebite victims, and to contribute to the haemotoxic profile of venomous snakes.Nrf Postgraduate scholarshipPhysiologyMSc (Human Physiology)Unrestricte
The effect of aspirin and lipopolysaccharide binding protein on hypercoagulability induced by lipopolysaccharide
Full text linkThesis (PhD (Human Physiology))--University of Pretoria, 2019.Inflammation is a well-known underlying cause in many diseases. Chronic inflammation has a role in a host of common and often deadly diseases, including Alzheimer’s disease, rheumatoid arthritis, cancer, type 2 diabetes, heart disease, and even conditions like depression. A highly potent inflammagen might be one of the drivers of systemic inflammation, when present in circulation and it is the bacterial component called Lipopolysaccharide. It is known that lipopolysaccharide is located on the outer membrane of gram-negative bacteria. Recently, research has shown that this bacterial (and other) membrane components, when in circulation, might have a direct effect on blood hypercoagulability, which is a prominent hallmark of chronic, systemic inflammation. In this study it is shown that Lipopolysaccharide caused marked changes in the nature of the fibrin network formed. Furthermore, irregular red blood cells’ membrane, platelets activation and formation of microparticles were seen when examining with scanning electron microscope and confocal microscope. Addition of Lipopolysaccharide caused significant hypercoagulation and changes to viscoelasticity of whole blood, as noted using Thromboelastograph. Airyscan confocal microscopy was used to study abnormal fibrin(ogen) protein folding in the presence of Lipopolysaccharide, using a well-known amyloid protein marker of anomalous blood protein clotting, called Thioflavin T. Previously, it was shown that this anomalous clotting of fibrin(ogen) fibres is amyloid in nature. Mopping agents are needed to reverse the hypercoagulation induced by Lipopolysaccharide. Biochemical agents (mopping agents) that will prevent anomalous blood clotting are therefore needed to reverse the hypercoagulation induced by Lipopolysaccharide. Such agents could, in future be used to prevent anomalous clotting in inflammatory diseases, where increased Lipopolysaccharide levels are known to be present.
The first Lipopolysaccharide mopping agent of choice is Lipopolysaccharide binding protein. The Lipopolysaccharide binding protein is a serum molecule that arbitrates cellular activation in reaction to endotoxin by ensuring the delivery of Lipopolysaccharide to either soluble or membrane bound forms of CD14 also known as mCD14. The second Lipopolysaccharide mopping agent in this study, is aspirin. Aspirin is an anticoagulant and commonly used anti-inflammatory agent. In literature aspirin has been found to increase fibrin clot porosity and susceptibility to lysis. Lipopolysaccharide binding protein, and the combination with aspirin, and the effects on anomalous blood clotting, is novel, and has not previously been studied. The research questions that this thesis thus aims to address is, at what minimal concentration can the mopping agent Lipopolysaccharide binding protein be used to effectively “mop up” Lipopolysaccharide, and can Lipopolysaccharide binding protein be used in combination with Aspirin, an anticoagulant agent, to reduce the signs of hypercoagulation produced by Lipopolysaccharide ex vivo? Which techniques can be used to visually see the difference in structure and elastic function of fibrin(ogen) as well as cells in the coagulation system, namely red blood cells and platelets?
The results shown here reveal that Lipopolysaccharide binding protein can reduce the effect of Lipopolysaccharides on fibrin(ogen) and cells of the coagulation system at an exposure concentration of 2ng.L-1. The coefficient of variation from Airyscan confocal between control and treatments indicated a decrease in the intensity of samples treated with Lipopolysaccharide binding protein mixed with Lipopolysaccharide and a decrease in intensity from whole blood treated with aspirin compared to control (p=0.0106). The coefficient of variation calculated from Scanning electron microscopy, showed a distinct alteration in the clots from samples treated with Lipopolysaccharide binding protein and aspirin alone and mixed together gave (more variation of light coming from fibres, neatly branched forming three layers) as significant difference, when aspirin was mixed with Lipopolysaccharide showed less variation light from fibres fussed into one layer with the contact surface and the same with aspirin mixed with Lipopolysaccharide (less light variation) compared to the control (untreated PPP) (p<0.0001).
From the Thromboelastography® results there was a statistically significant differences in clot strength between whole blood and whole blood mixed with Lipopolysaccharide binding protein and Lipopolysaccharide, (p=0.0412). This shows a decrease in platelet and/or fibrin(ogen) interaction resulting in a less dense clot that is less rigid in fibrinogen or platelets. The time from clot initiation to maximum clot formation decreased when whole blood was mixed with aspirin together with Lipopolysaccharide binding protein and Lipopolysaccharide as compared with naïve whole blood, (p=0.0071). This usually occurs in hypercoagulation seen by decreased time from clot initiation to maximum clot formation. The amount of thrombus total resistance decreased significantly when whole blood was mixed with aspirin and Lipopolysaccharide verses whole blood alone, (p=0.0078). This shows that the addition of aspirin to Lipopolysaccharide can lead up to hypocoagulable state were the clot strength decreases. When measuring fibre thickness it was found that Lipopolysaccharide binding protein alone and in combination with aspirin effectively reduced the large fibres produced by Lipopolysaccharide, almost back to normal size which is +-110nm. The difference was statistically significant (p<0.05).
Lipopolysaccharide binding protein and aspirin showed impeccable results reducing the signs of Lipopolysaccharide-induced hypercoagulation, both in plasma and whole blood. Many non-communicable diseases have been shown to have a bacterial component. The amyloid protein created with Lipopolysaccharide, can be reversed in the blood model with the study’s novel combination of Lipopolysaccharide binding protein/aspirin could be implemented in applications for treatment of conditions where there is presence of Lipopolysaccharide particularly sepsis.PhysiologyPhD (Human Physiology)UnrestrictedFaculty of Health Science
The effect of the ex vivo addition of vitamin D on the prothrombotic and fibrinolytic potential in prostate cancer patients' blood.
Full text linkDissertation (MSc (Human Physiology))--University of Pretoria, 2022.Cancer and its consequences are amongst the major causes of death worldwide.
Prostate cancer (PCa) is the most frequent non-cutaneous malignancy in men
globally, with South Africa having the fourth highest prostate cancer mortality rate in the world. Patients diagnosed with PCa have been found to have a hypercoagulable state as a result of the elevated systemic inflammation that is a hallmark of cancer. Vitamin D supplementation has been shown in recent studies to improve the survival rates of individuals with PCa due to its anti-tumorigenesis properties. Given the link between chronic inflammation, hypercoagulation and PCa survival rates, improving the thrombotic status of PCa patients could be beneficial in the management of these patients.
This study investigated the hypercoagulable state of both metastatic and nonmetastatic PCa patients, in comparison to a reference group, before and after the ex vivo supplementation with vitamin D. The morphological and viscoelastic properties of whole blood and platelet poor plasma were investigated using light microscopy, scanning electron microscopy and thromboelastography®.
This study indicated that vitamin D supplementation might potentially aid the pathology caused by abnormal RBC shape, albeit caution should be used in metastatic PCa populations since supplementation was seen to result in a tendency to create stronger, more rigid clots at a faster pace. Although vitamin D supplementation shows potential as a more cost-effective therapy regime for the elevated thrombotic risk commonly seen in individuals with PCa, additional research is needed to determine the impact of vitamin D supplementation on hypercoagulability in vivo.National Research Foundation (NRF)PhysiologyMSc (Human Physiology)Unrestricte
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