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Biomedical subjects

S Sivaloganathan

Publications and source records attributed to S Sivaloganathan.

At least 19 recordsLinked to original sources
PubMed2006

Mathematical modeling of ovarian cancer treatments: sequencing of surgery and chemotherapy.

Ovarian cancer has long been one of the most common forms of cancer in women. The main treatment for ovarian cancer comprises a combination of surgery and chemotherapy. In an effort to improve treatment strategies, a variety of mathematical models have been developed in the literature. In this paper, we consider a simple mathematical model that incorporates tumor growth as well as the effects of chemotherapeutic and surgical treatments in ovarian cancer. We consider several growth models and combine them with different cell-kill hypotheses. Surgery is assumed to eliminate a fixed fraction of tumor cells instantaneously. We discuss how different models predict the optimal sequencing of chemotherapeutic and surgical treatments. This work has been carried out in the context of ovarian cancer; however, the results may also be useful for other kind of cancers.

Antineoplastic Agents↗
PubMed2005

The constitutive properties of the brain parenchyma Part 1. Strain energy approach.

In this paper we study several constitutive equations for the brain based on the strain energy density function. We use the polynomial function and hyper-elastic Ogden model for the strain energy and include the energy dissipation by a Prony series expansion. The models are compared with known unconfined compression experimental results of the human brain tissue to obtain the best fitted model and brain mechanical parameters. Finite element simulations are also performed using the given constitutive equations, and numerical solutions match the analytical results very closely. The results are compared with other analytical and numerical calculations.

Algorithms↗
PubMed2005

The constitutive properties of the brain paraenchyma Part 2. Fractional derivative approach.

Fractional models have proven to be very useful for studying viscoelastic materials. We consider the fractional Zener model (also called four-parameter model) to study both the relaxation function and creep compliance. The analytical results are compared with the known experimental results of the human brain tissue to obtain the best fit and brain mechanical parameters. The results are also compared to the non-fractional Zener model and four-parameter Burgers model, indicating that the four-parameter fractional model gives a substantially better fit for the all experimental data.

Algorithms↗
PubMed2005

Frequency dependence of complex moduli of brain tissue using a fractional Zener model.

Brain tissue exhibits viscoelastic behaviour. If loading times are substantially short, static tests are not sufficient to determine the complete viscoelastic behaviour of the material, and dynamic test methods are more appropriate. The concept of complex modulus of elasticity is a powerful tool for characterizing the frequency domain behaviour of viscoelastic materials. On the other hand, it is well known that classical viscoelastic models can be generalized by means of fractional calculus to describe more complex viscoelastic behaviour of materials. In this paper, the fractional Zener model is investigated in order to describe the dynamic behaviour of brain tissue. The model is fitted to experimental data of oscillatory shear tests of bovine brain tissue to verify its behaviour and to obtain the material parameters.

Animals↗
PubMed2000

Brain biomechanics: mathematical modeling of hydrocephalus.

The considerable amount of literature on mathematical models of hydrocephalus and other brain abnormalities is critically reviewed. These models have various degrees of mathematical sophistication, and have influenced not only the diagnosis of hydrocephalus, but also its treatment with CSF shunts. The mathematical models are classified into two classes, pressure-volume models, and consolidation models. Advantages and disadvantages of both types are pointed out with a view to removing the confusion frequently generated by the technical aspects of the subject. The conclusion is reached that, while none of the current models are good enough to be of immediate use to the neurosurgeon, mathematical models are likely in the future to be a powerful tool for the understanding and the treatment of hydrocephalus, as well as other conditions related to brain biomechanics. The amount of mathematics has been kept to the absolute minimum, but it is cited and appended for those who would like to dig further into this fascinating area of research.

Biomechanical Phenomena↗
PubMed1999

Correlation of survival time with size of axonal swellings in diffuse axonal injury.

Widespread damage to axons in the white matter of the brain is a well-recognised consequence of non-missile head injury. This diffuse axonal injury is characterised by a gradual swelling of the axon associated with an accumulation of cellular organelles and proteins. We have investigated the relationship between the size of the swellings of the damaged axon with survival time in post-mortem brain tissue. Sixty-six cases of head injury with known length of post-traumatic survival were selected for study, and immunohistochemistry for beta-amyloid precursor protein (betaAPP) was carried out. The minimum diameter of the betaAPP-immunolabelled damaged axons was measured in micrometers using the IBAS image analysis system. There was a strong, positive and significant relationship between the mean size of axonal swelling and survival time which plateaued at around 85 h post injury. With longer survival times the situation becomes more complex. betaAPP immunolabelling of damaged axons can contribute evidence about trauma and post-injury survival time in the forensic setting but should always be assessed with other evidence.

Adolescent↗
PubMed1998

Death from diesel fumes.

A rare fatality from inhalation of diesel motor exhaust fumes is reported and the toxicity of diesel fumes is discussed briefly.

Journal Article↗
PubMed1995

Medical evidence for the defence in homicide trials.

The legal system for the investigation of major crime appears to be rather loose, in that there are no specific statutory provisions available to a defendant to present his or her case properly and adequately in court. There are no guidelines issued to the coroners nor are there any legal powers available to them to facilitate and authorize post-mortem examinations on behalf of the defence. This paper focuses attention on this legal dilemma, and attempts to suggest possible remedies.

Forensic Medicine↗
PubMed1994

Early detection of axonal injury after human head trauma using immunocytochemistry for beta-amyloid precursor protein.

Severe non-missile head injury commonly results in a form of brain damage known as diffuse axonal injury (DAI). The histological diagnosis of DAI is made by silver staining for the presence of axonal retraction balls. This feature takes about 24 h to develop and does not allow for the early histological diagnosis of DAI. We have used immunocytochemistry for the beta-amyloid precursor protein (beta APP) as a marker for axonal injury in formalin-fixed, paraffin-embedded sections of human brain. Axonal beta APP immunoreactivity was present in all cases which had survived for 3 h or more. This was true even where the degree of head injury did not appear to be severe, supporting the theory that DAI is a severe form of a more common phenomenon of axonal injury which occurs after cerebral trauma. beta APP immunoreactivity was also found in some non-head injured cases and so cannot be considered to be a specific marker for trauma. The results show that beta APP immunocytochemistry may be useful in the detection of traumatic axonal injury in its early stages, before the formation of axonal retraction balls, provided care is taken to exclude other causes of such immunoreactivity.

Adult↗
PubMed1994

Markers of axonal injury in post mortem human brain.

beta-Amyloid precursor protein (beta APP) can be detected immunocytochemically at sites of axonal injury in the brain, and has recently been found to be a useful marker for injured axons in patients who survived for only 3 h after head trauma. It is transported by fast axonal transport and is thought to accumulate in detectable levels where the cytoskeleton breaks down. If this theory is correct, other substances should accumulate here in the same way, so we have used antibodies to other neuronal proteins to compare their efficacy as markers of axonal injury. SNAP-25, chromogranin A and cathepsin D also marked injured axons at all survival times studied (2.5 h-2 weeks), although they were not as sensitive or specific as beta APP. Immunolabelling for the 68-kDa neurofilament subunit (NF68) was present in most uninjured axons, and allowed axonal swellings to be seen in some cases. Synaptophysin, GAP-43, ubiquitin or tau did not label any normal or injured axons in this study. We, therefore, suggest that beta APP should be the immunocytochemical marker of choice for the detection of injured axons. This study also showed that microwave antigen retrieval significantly enhances the immunoreactivity of SNAP-25, chromogranin A, synaptophysin, GAP-43, ubiquitin and tau, in addition to that of beta APP, in formalin-fixed, paraffin-embedded tissue, and reveals NF68 antigenicity where it was not previously detectable.

Adolescent↗
PubMed1992

Fabry's disease--a rare cause of sudden death.

A case of Fabry's disease, an X-linked in-born error of metabolism, presenting as a sudden death in an elderly female, is reported, along with a review of the literature. The pathological findings of the cellular vacuolation and the characteristic inclusion bodies in the tissues are described.

Aged↗
PubMed1989

Aspiration of high-density barium contrast medium causing acute pulmonary inflammation--report of two fatal cases in elderly women with disordered swallowing.

Two cases are reported in which accidental inhalation of barium contrast medium occurred owing to disordered swallowing in elderly women. In each case there was a pulmonary inflammatory reaction followed within a few hours by death. Experimental and clinical reports of barium inhalation are reviewed and the hazard of aspiration of high density barium preparations in elderly and debilitated patients with dysphagia is emphasised. It is concluded that particular care should be taken in the radiological examination of such patients, and a suggested method for performing a contrast swallow in those who are liable to aspirate is described.

Acute Disease↗
PubMed1989

The Bradford Fire Disaster. Part 2. Accident reconstruction: who died, when and why.

The circumstances of the Bradford Football Stadium Fire have been described in Part 1. Part 2 relates the positions in which the bodies were found, their carbon monoxide concentrations, and the physical configuration of the stand to the seat of the fire. It also examines the causes of the high death toll and makes recommendations for the future planning and management of sports stadiums.

Adolescent↗