De bloedsomloop door de nieren bij essentiële hypertensie

De nier neemt een sleutelpositie in bij de volumeregulatie in het menselijk lichaam. Door de uitscheiding van water en zout aan de omstandigheden aan te passen, kunnen dreigende veranderingen van het extracellulaire volume worden voorkomen. De vullingsgraad van een systeem bepaalt in hoge mate de daarin heersende druk. Vergroting van het extracellulaire volume zal mogelijk een rol kunnen spelen bij het ontstaan van bloeddrukverhoging. Onmisbaar in deze voorstelling van zaken is het optreden van water- en zoutretentie door de nier. Bij de volumeregulatie lijkt er in de nier een regionale taakverdeling te bestaan. De nefronen in de buitenste nierschors zouden vooral van betekenis zijn voor de water- en zoutuitscheiding, terwijl de juxtamedullaire nefronen door de lange lissen van Henle meer geschikt zijn voor volumeretentie. De nier kan ook als endocrien orgaan bij de regulering van de bloeddruk betrokken zijn. Door productie van renine wordt angiotensine !I vrijgemaakt. Dit peptide is de sterkst bloeddrukverhogende stof bekend in de fysiologie. Het renine-angiotensine systeem is door het stimuleren van de aldosteronproductie nauw verbonden met de volumeregulatie. Vele gegevens wijzen op het bestaan van een wisselwerking tussen het renine-angiotensine systeem en de haemodynamische verhoudingen in de nier. Terwijl de renineproductie vooral plaats vindt in de buitenste nierschors, wordt in het niermerg prostaglandine A2 gemaakt, een stof met bloeddrukverlagende eigenschappen

Buckling of laser-welded sandwich panels : ultimate strength and experiments

This is the last of three companion papers which examine the elastic buckling and collapse of laser-welded sandwich panels with an adhesively bonded core and unidirectional vertical webs. By evaluation of the buckling stress in the first two papers it has been found that the buckling stress in compression parallel and normal to the webs typically reaches the proportional limit of the face plate and web material well before elastic buckling occurs. Hence, this paper presents an extension of the buckling model into the elastoplastic regime, with the aim of determining the ultimate (local) strength of the sandwich and of allowing experimental verification of the results. Using tangent modulus theory to 'plasticize' the elastic buckling model, the ultimate strength is evaluated for a sandwich configuration with high-strength steel face plates and a broad range of core moduli. The critical load predicted by the inelastic buckling model agrees well with non-linear finite element results and experimental values obtained from compression testing.QC 20111104</p

Neoadjuvant chemotherapy in oesophageal cancer

Neoadjuvant chemotherapy in oesophageal cancer has gained rapid favour in le United Kingdom over the past few years. It remains controversial outside the UK, with mixed results from clinical trials. The work in this thesis begins with a review of the literature on neoadjuvant chemotherapy, and of the antimetabolites and platinum agents used. The quantitative reverse transcriptase polymerase chain reaction (qRTPCR) used to identify molecular determinants of chemosensitivity is discussed followed by a look at the clinical experience of neoadjuvant chemotherapy at a single centre. Over the past six years 194 patients in Oxford have undergone neoadjuvant chemotherapy with cisplatin and 5-flurouracil. Six patients developed progressive disease, 12 patients stopped chemotherapy early, one patient died during chemotherapy and one patient had perforation of the oesophagus. Overall chemotherapy was well tolerated among patients with no significant increase in respiratory complications and anastomotic leak following the use of neoadjuvant chemotherapy. Following the advent of neoadjuvant chemotherapy, there has been a significant decrease in circumferential resection margin involvement, compared to historical controls. Locoregional recurrence and overall survival have also improved. Cox's multivariate analysis shows circumferential resection margin to be an independent prognostic factor for locoregional recurrence and overall survival.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Aortic and peripheral blood pressure during isometric and dynamic exercise

The purpose of this study was to compare aortic blood pressure (AOR) to peripheral measurements by the Riva-Rocci/Korotkov (RRK) and Finapres continuous finger pressure (FIN) methods during dynamic and static exercise. A tip manometer was introduced in the ascending aorta after coronary angiography in 7 cardiac patients with good exercise capability. Static exercise was of moderate intensity and led to an increase of average diastolic and systolic AOR of 20 and 18 mmHg, respectively. The corresponding RKK values were 20 and 30 mmHg and the FIN values were 16 and 14 mmHg, respectively. In maximal cycle ergometry the discrepancies were larger, especially in the 4 subjects who reached 80% or more of predicted maximal work load, Diastolic and systolic increases in AOR in these 4 subjects were 12 and 38 mmHg, respectively. The RRK values were 17 and 76 mmHg. Increases in FIN values of 17 and 74 mmHg for diastolic and systolic measurements, respectively, were found. The peripheral FIN and RRK measurements give a systolic increase that is twice as large as that for AOR. It is concluded that RRK and FIN greatly overestimate the load to the cardiovascular system in dynamic exercise. When the cardiovascular load is estimated by the rate-pressure product, RRK produces an increase of 197%, FIN of 181%, while AOR gives an increase of only 133%. This suggests that the present criteria for blood pressure in exercise testing should be critically examined