Academic Ceremonies January 2012

“The Three-dimensional Substrate of Atrial Fibrillation in the Goat”

Atrial fibrillation (AF) is the most common arrhythmia in humans and Maastricht is a reference center for mapping of AF. Mapping is a technique to visualize the electrical activity of the atrial muscle. In earlier studies this was performed solely on the outer (epicardial) surface of the atrium. In this thesis we describe a novel technique and findings of simultaneous, endo-epicardial mapping. We could show that, while electrical activity during normal rhythm is synchronous at the inside and the outside of the atrium, it is getting increasingly dissociated if AF is present for a longer time (weeks to months). Along with this we could demonstrate that so called breakthrough events, that represent focal activations in two-dimensional mapping, are explainable by transmurally propagated electrical activity from the opposing side of the atrial wall in most cases. These findings help to understand what makes AF increasingly stable and harder to treat over time.

Key words:

atrial fibrillation, mapping, endo-epicardial dissociation

“Transcutaneous electrical nerve stimulation for patients with chronic pain”

“Learning in Urology; the influence of simulators and human factors”

“The dynamics of production in advance; three essays in how pre-made decisions on inventory can influence revenue-maximization and the nature of competition”

“Where the drug meets the road: actual driving, psychomotor performance and roadside drug screening methods in cannabis and ecstasy users”

Driving under the influence of drugs can affect the driving ability. This dissertation studies the interface between road safety and the use of ecstasy and cannabis.  THC (the active substance in cannabis) in the form of pills and the combination of lack of sleep and ecstasy appeared to negatively influence the driving ability. The ‘Standardized Field Sobriety Tests’ that are used on the roadside in North America to show decreased driving ability as a result of alcohol use, turned out insensitive to this form of THC. Saliva testing appeared not 100% suitable for reliable detection of THC, but this method has strongly improved over the last few years and appears promising for the screening of drivers for drug use.  

Key words:

drugs, driving ability, saliva testing, Standardized Field Sobriety Tests

“Diacylglycerol: an innocent bystander in skeletal muscle insulin resistance?”

Overweight involves fat accumulation in muscles and this phenomenon is associated with the development of insulin resistance, the pre-stage of type 2 diabetes. This dissertation studies the molecular mechanisms of fat induced insulin resistance, with particular attention to the role of diacylglycerol in this process. Diacylglycerol is a side-product of fat metabolism that accumulates in the muscle when the balance between fat absorption and fat burning is disturbed.   Using various research models (nutritional, pharmacological and genetic interventions) in test animals and persons the fat metabolism in the muscle is modified to analyse the role of diacylglycerol in insulin resistance of the muscle. One of the conclusions is that this cannot be explained by merely taking into account the quantity of diacylglycerol that is accumulated.

Key words:

overweight, insulin resistance, fat metabolism, diacylglycerol

“Economic consequences of public oversight of the audit market”

“Alcohol Consumption in Relation to Cardiovascular Risk and Mortality”

It is known that drinking alcohol in moderation is associated with reduced cardiovascular disease and total mortality in healthy subjects, whereas its abuse is unquestionably harmful. This thesis has confirmed previous studies in healthy people and has extended them to the association of alcohol consumption with cardiovascular and total mortality in cardiovascular patients. Highly sophisticated statistical analyses have been used to dissect the issue. In both healthy subjects and cardiovascular patients, teetotalers and heavy drinkers are at the highest risk whereas light-moderate drinkers are at the lowest risk. A similar relationship was found when either wine or beer consumption were considered. In conclusions: there is no reason to discourage either healthy persons or cardiovascular patients, if they are regular light-moderate alcohol consumers from continuing. Heavy or binge drinkers should always be urged to cut and modify their consumption.

Key words:

alcohol, cardiovascular disease, risks

“Interventional therapy in complex regional pain syndrome type 1: Predicting the outcome”

“Connecting the dots; new perspectives on stress and psychosis”

Psychotic disorders, among which schizophrenia, belong to the most paralyzing and elusive psychiatric diseases. Although it is assumed that stress plays an important role in the development of psychotic experiences, by far not everyone becomes psychotic after a stressful event. This dissertation studies why one person does and the other doesn’t react psychotically to stress – which mechanisms are involved there? One of the conclusions is that dopamine stress handling in the brains of persons with psychotic vulnerability shows defects – a defect that is partly ‘family-related’, but on the other hand may be stirred up by repeated exposure to radical stressful events.  

Key words:

psychotic disorder, schizophrenia, stress, dopamine

“Human Thermoregulation; A synergy between physiology and mathematical modeling”

This dissertation studies the regulation of the body temperature in both young and old people. Both the skin blood flow (regulation and heat release) and the energy use (heat production) were studied in a cool environment. In old people the core temperature went down, in contrast to the young people. There was, however, no difference in the change of the skin blood flow. On the other hand, young people increased the heat production, whereas that decreased in the elderly. Also, the blood pressure increased three times as much in the elderly as it did in the young people. The newly developed mathematical model shows that the decrease of heat production in the elderly is caused by cooling of the body. As opposed to young people, elderly people lose the capacity to compensate this decrease.

Key words:

body temperature, mathematical models, metabolism, skin blood flow