Quantification of friction force reduction induced by obstetric gels

The objective of this study was to quantify the reduction of friction forces by obstetric gels aimed to facilitate human childbirth. Lubricants, two obstetric gels with different viscosities and distilled water, were applied to a porcine model under mechanical conditions comparable to human childbirth. In tests with higher movement speeds of the skin relative to the birth canal, both obstetric gels significantly reduced dynamic friction forces by 30-40% in comparison to distilled water. At the lowest movement speed, only the more viscous gel reduced dynamic friction force significantly. In tests modifying the dwell time before a movement was initiated, static friction forces of trials with highly viscous gel were generally lower than those with distilled water. The performed biomechanical tests support the recommendation of using obstetric gels during human childbirth. Using the presented test apparatus may reduce the amount of clinical testing required to optimize gel formulatio

PKA and EPAC: cyclic AMP effectors in the regulation of myometrial inflammatory responses in parturition

The timing of parturition is key to a successful conclusion of pregnancy. For births that occur before 37 weeks, which is defined as preterm birth (PTB), the baby is at increased risk of neonatal morbidity and mortality. PTB remains a significant public health concern, affecting around 1 in 10 births worldwide. The initiation of parturition is caused by an accumulation of factors that promote myometrial contractions, and inflammation is often proposed to be one such factor. At the same time, it is also proposed that a withdrawal of signalling pathways that support myometrial quiescence is sufficient to trigger parturition. Progesterone is most recognised for this role in maintaining myometrial quiescence. There is also ample evidence to suggest that cAMP signalling also plays a role. Recent published studies have suggested that PKA can enhance the effects of progesterone and suppress myometrial inflammatory responses. Additionally, a pro-contractile role for cAMP via EPAC-mediated pathways has also been proposed. The overall aim for this thesis was to investigate the role of cAMP in the regulation of myometrial inflammatory responses in the context of parturition. Using primary myometrial cells cultured from human myometrial biopsies, which were all obtained from term gestation non-labouring study participants at time of elective/planned Caesarean section, my studies demonstrated that cAMP’s anti-inflammatory effects are mediated by PKA. PKA-specific activator N6-benzoyl-cAMP (6-Bnz-cAMP) suppressed myometrial expression of IL-8 in response to IL-1β stimuli. Furthermore, siRNA knockdown of catalytic PKA subunit (PKAc) partially reduced forskolin’s ability to suppress IL-8 expression. My data also showed forskolin’s ability to reduce NF-κB translocation is lost in the event of PKAc knockdown. The role of EPAC was investigated using EPAC activator 8-pCPT-2'-O-Me-cAMP and inhibitor ESI-09. My experiments showed EPAC activation was able to increase phosphorylation of MEK1/2, and downstream p65 Ser 536 phosphorylation. However, this did not further increase IL-8 expression. Most interestingly, the EPAC inhibitor reduced extracellular IL-8 concentrations but increased levels of IL-8 mRNA and intracellular protein, which suggests EPAC has a role in regulating IL-8 secretion. Finally, using a genetically modified hTERT-HM myometrial cell line that can express inducible progesterone receptor A (PR-A) and B (PR-B), I examined the impact of EPAC signalling on PR-A phosphorylation and total protein abundance. Using 8-pCPT-2'-O-Me-cAMP, the findings from my data suggested that an EPAC-mediated increase in JNK activity can result in both an increase in PR-A Ser 345 phosphorylation and total protein levels. This suggests EPAC can promote PR-A dominance, which is a well-recognised feature of the progesterone functional withdrawal concept that is often used to explain how human parturition is initiated. In summary, the work presented here provides evidence that PKA and EPAC have distinct contributions to myometrial inflammatory response at cellular level. Further study of how their roles coordinate with each other to control the dynamics of myometrial cAMP signally will add depth to our understanding of the molecular processes that support myometrial quiescence or enhance myometrial contractility.Open Acces

Mechanoresponsive drug delivery materials

Stimuli-responsive drug delivery materials release their payloads in response to physiological or external cues and are widely reported for stimuli such as pH, temperature, ionic strength, electrical potential, or applied magnetic field. While a handful of reports exist on materials responsive to mechanical stimuli, this area receives considerably less attention. This dissertation therefore explores three-dimensional networks and polymer-metal composites as mechanoresponsive biomaterials by using mechanical force to either trigger the release of entrapped agents or change the conformation of implants. At the nanoscale, shear is demonstrated as a mechanical stimulus for the release of a monoclonal antibody from nanofibrous, low molecular weight hydrogels formed from bio-inspired small molecule gelators. Using their self-healing, shear-thinning properties, mechanoresponsive neutralization of tumor necrosis factor alpha (TNFα) in a cell culture bioassay is achieved, suggesting utility for treating rheumatoid arthritis. Reaching the microscale, mechanical considerations are incorporated within the design of cisplatin-loaded meshes for sustained local drug delivery, which are fabricated through electrospinning a blend of polycaprolactone and poly(caprolactone-co-glycerol monostearate). These meshes are compliant, amenable to stapling/suturing, and they exhibit bulk superhydrophobicity (i.e., extraordinary resistance to wetting), which sustains release of cisplatin >90 days in vitro and significantly delays tumor recurrence in an in vivo murine lung cancer resection model. This polymer chemistry/processing strategy is then generalized by applying it to the poly(lactide-co-glycolide) family of biomedical polymers. As a macroscopic approach, a tunable, tension-responsive multilayered drug delivery device is developed, which consists of a water-absorbent core flanked by two superhydrophobic microparticle coatings. Applied strain initiates coating fracture to cause core hydration and subsequent drug release, with rates dependent on strain magnitude. Finally, macroscopic, shape-changing polymer-composite materials are developed to improve the current functionality of breast biopsy markers. This shape change provides a means to prevent marker migration from its intended site—a current clinical problem. In summary, mechanoresponsive systems are described, ranging from the nano- to macroscopic scale, for applications in drug delivery and biomedical devices. These studies add to the nascent field of mechanoresponsive biomedical materials and the arsenal of drug delivery techniques required to combat cancer and other medical ailments.2017-10-27T00:00:00

The use of Fluid Haemodynamics in the Diagnosis of Cardiovascular Disease

Currently the diagnostic methods used to detect cardiovascular disease largely rely on the inference of the presence of arterial stenosis. There is a clinical interest in the development of a diagnostic screening technique which can indicate the risk of developing cardiovascular disease at an early stage so that non-surgical treatments can be applied. The goal of this work was to develop and validate a diagnostic screening technique for cardiovascular disease using the mechanical biomarker wall shear stress. Improvements in wall shear stress measurements were made by using a 2D Fourier transform to extract additional spectral information from the ultrasound pulse and decrease the spectral variance by integrating across the bandwidth of transmitted frequencies. This technique was validated for a series of anatomically realistic flow phantoms which precisely mimicked the progression of wall stiffening that characterises cardiovascular disease. The newly developed spectral analysis technique demonstrated a higher diagnostic performance than the other techniques tested, both in terms of a greater degree of significance in detecting differences in vessel wall stiffness and in terms of the sensitivity and specificity of the technique. The technique could not be tested in pulsatile flow due to hardware limitations, but preliminary testing indicated that the increased performance of the technique would likely transfer to a physiological flow regime. The results of this work indicated that the algorithm had the potential to rival the diagnostic power of the current gold standard while being applicable at an earlier stage of cardiovascular disease

Applications of EMG in Clinical and Sports Medicine

This second of two volumes on EMG (Electromyography) covers a wide range of clinical applications, as a complement to the methods discussed in volume 1. Topics range from gait and vibration analysis, through posture and falls prevention, to biofeedback in the treatment of neurologic swallowing impairment. The volume includes sections on back care, sports and performance medicine, gynecology/urology and orofacial function. Authors describe the procedures for their experimental studies with detailed and clear illustrations and references to the literature. The limitations of SEMG measures and methods for careful analysis are discussed. This broad compilation of articles discussing the use of EMG in both clinical and research applications demonstrates the utility of the method as a tool in a wide variety of disciplines and clinical fields

Improving Electrical Impedance Tomography of brain function with a novel servo-controlled electrode helmet

Electrical Impedance Tomography (EIT) is a medical imaging technique which reconstructs the internal conductivity of an object from boundary measurements. EIT has the potential to provide a novel means of imaging in acute stroke, epilepsy or traumatic brain injury. Previous studies, whilst demonstrating the potential of the technique, have not been successful clinically.The work in this thesis aims to address fundamental limitations including measurement drift in electronic hardware, lack of an anatomically realistic tank phantom for rigorous testing, poor electrode-skin contact and mis-location of scalp electrodes. Chapter 1 provides an introduction of the principles of bioimpedance and EIT, as well as a review of previous clinical studies. Chapter 2 details the development of a novel anatomically realistic head phantom, simulating the human adult head with scalp electrodes, using a 3D printer and cylindrical holes to provide simulated conductivity. This replicated the varying spatial conductivity of the skull within 5 % of the true value. Two multifrequency EIT systems with parallel voltage recording were optimised for recording in the adult head with scalp electrodes, in chapter 3. Measurement drift was reduced by better case design and temperature control and data quality was improved with an updated interface to the current source and signal processing. The UCL ScouseTom system, performed best, with lower noise in all resistor and tank measurements, but the differences were masked during scalp recordings. Further, both systems produced similar results in the realistic adult head tank from chapter 2. Recent advances in EIT imaging coupled with the developments in chapters 2 and 3 provided opportunity to reassess the feasibility of monitoring epilepsy with EIT. Biologically representative perturbations was localised to within 8 mm in the head tank, with less than half the image error of previous studies. However, the key limitations of application time and measurement drift with scalp electrodes had yet to be addressed. Therefore the focus of the work in chapter 5 and chapter 6 was the design and testing of a novel self-adjusting electrode helmet. Skin-electrode impedance was continuously optimised by constant pressure, rotation and feedback control, and position sensors returned the co-ordinates of electrode tips. Finally, experiments with this helmet were undertaken to assess the feasibility of future clinical recordings

Investigating the chondrogenic phenotype in clinically relevant cells: the effect of hTERT expression

Damaged or diseased mature articular cartilage cannot undergo effective tissue repair and due to its avascular, hypocellular nature defects become widespread and painful. No ‘gold standard’ treatment exists for this indication and the ultimate recourse is prosthetic joint replacement. Cartilage is therefore an ideal target for regenerative medicine therapies aiming to recapitulate native cartilage. Despite over fifty years of research and encouraging outcomes, re-creation of the hyaline tissue has yet to be consistently achieved, possibly as a result of the application of a sub-optimal cell type. Chondrocytes and bone marrow mesenchymal stem cells (MSCs) have been used clinically, with future prospects for other alternative MSC sources and human embryonic stem cell (hESC)-derived cells. Further in vitro study of cellular chondrogenic capacity is desirable but hampered by cell changes and senescence. This work examines the hypothesis that the re-introduction of the catalytic sub-unit human telomerase reverse transcriptase (hTERT) can extend the proliferative cell capacity of cells whilst concomitantly bypassing changes associated with cell aging and senescence. The utility of umbilical cord blood (UCB) as a possible alternative source of more naive MSCs was also investigated. Human bone marrow MSCs, chondrocytes, and hESC-derived cells were transduced with hTERT and their resulting chondrogenic capacity, assessed principally by extracellular matrix (ECM) production and gene expression, examined and compared to that of the three non-transduced, parental cell sources. UCB was not found to be a viable alternative MSC source due to a very low cell number and colony recovery; however, foetal bovine serum (FBS) batch and atmospheric oxygen tension were identified as key to influencing recovery outcomes. Of the three parental cell types examined for chondrogenic potential MSCs and chondrocytes produced similar amounts of sGAG but chondrocytes produced a more homogeneous ECM with persistent chondrogenesis, whereas MSCs became hypertrophic. hESC derived cells had a more muted chondrogenic response with similarities to both chondrocytes and MSCs. TERT extended the proliferative capacity of all three cell types, two extensively but was also associated with changes in cell phenotype and a reduction, although not complete ablation, in the subsequent chondrogenic capacity. Taken together the results demonstrate that with current differentiation techniques primary articular chondrocytes provide the most optimal result, supporting their continued use for clinical therapies, and this capacity may not be preserved by the application of hTERT transduction strategies

Ultrasound and magnetic resonance techniques for the haemodynamic quantification of the peripheral vascular system

The aim of this thesis was to determine whether the blood flow velocities in the peripheral vascular system measured using phase contrast magnetic resonance imaging, PC-MRI, techniques could be used in the same way that blood flow velocities measured using spectral Doppler ultrasound are used to aid in the diagnosis of peripheral vascular disease. Specifically, we aimed to investigate the measurement of maximum velocities and the use of maximum velocity ratios; an area of investigation which has been neglected in studies of PC-MRI blood flow quantification to date. A series of optimisation and comparison studies were carried out using in-house developed test phantoms. Key to the in-vitro work was the establishment of a dual modality flow test system which would allow comparison of identical flow conditions measured using ultrasound and MRI. The work was complemented by in-vivo studies in healthy volunteers. A 4D PC-MRI commercial work-in-progress protocol and software package became available during the study and was evaluated in-vitro and in-vivo using similar methods as for the 2D PC-MRI studies. The main findings of the thesis were that 2D PC-MRI measurement of maximum velocities significantly underestimated those measured using spectral Doppler ultrasound. However, if corrections were applied to account for the overestimation of ultrasound maximum velocity due to spectral broadening, then the two methods were in agreement. In contrast, the use of maximum velocity ratios showed no difference between spectral Doppler ultrasound and 2D PC-MRI measurements. It was noted that one of the potential problems with the use of 2D PC-MRI in the measurement of the maximum velocity at a stenosis is the accurate positioning of the 2D velocity encoded slice in the stenotic jet. 4D PC-MRI, with a time resolved velocity encoded volume dataset, offers a potential solution to this. However, our evaluation of 4D PC-MRI showed that it can significantly underestimate both maximum velocities and maximum velocity ratios in comparison with 2D PC-MRI and spectral Doppler ultrasound and requires further development before it can be used for peripheral vascular applications