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Biomedical subjects

J R Blake

Publications and source records attributed to J R Blake.

At least 19 recordsLinked to original sources
PubMed2006

A viscoelastic traction layer model of muco-ciliary transport.

A new mathematical model of the transport of mucus and periciliary liquid (PCL) in the airways by cilia is presented. Mucus is represented by a linearly viscoelastic fluid, the mat of cilia is modelled as an 'active porous medium.' The propulsive effect of the cilia is modelled by a time-dependent force acting in a shear-thinned 'traction layer' between the mucus and the PCL. The effects of surface and interface tension are modelled by constraining the mucus free surface and mucus-PCL interface to be flat. It is assumed that the epithelium is impermeable to fluid. Using Fourier series, the system is converted into ODEs and solved numerically. We calculate values for mean mucus speed close to those observed by Matsui et al. [J. Clin. Invest., 102(6):1125-1131, 1998], (approximately 40 microm s(-1)). We obtain more detail regarding the dynamics of the flow and the nonlinear relationships between physical parameters in healthy and diseased states than in previously published models. Pressure gradients in the PCL caused by interface and surface tension are vital to ensuring efficient transport of mucus, and the role of the mucus-PCL interface appears to be to support such pressure gradients, ensuring efficient transport. Mean transport of PCL is found to be very small, consistent with previous analyses, providing insight into theories regarding the normal tonicity of PCL.

Cilia↗
PubMed2001

Enhanced efficiency of feeding and mixing due to chaotic flow patterns around choanoflagellates.

The motion of particles and feeding currents created by micro-organisms due to a flagellum are considered. The calculations are pertinent to a range of sessile organisms, but we concentrate on a particular organism, namely Salpingoeca amphoridium (SA) (a choanoflagellate), due to the availability of experimental data (Pettitt, 2000). These flow fields are characterized as having very small Reynolds numbers, which implies that viscous forces dominate over inertial ones consistent with using the Stokes flow equations. The flow generated by the flagellum is modelled via the consideration of a point force known as a stokeslet. The interaction between the boundary, to which the organism is attached, and its flagellum leads to toroidal eddies, which serve to transport particles towards the micro-organism, promoting filtering of nutrients by the microvilli which constitute the cell's collar (the filtering mechanism in SA). It is our conjecture that the interaction of multiple toroidal eddies will lead to chaotic advection and hence enhance the domain of feeding for these organisms. The degree of mixing in the region around SA is investigated using chaotic and statistical measures to study the influence the flagellum has on the surrounding fluid. The three-dimensional particle paths around such organisms are also considered with the aim of showing that the plane within which they are situated is an attractor.

Animals↗
PubMed1995

Hydrodynamics of filter feeding.

A fluid mechanical model is developed for the filtering mechanism in mussels that enables estimates to be made of the pressure drop through the gill filaments due to (i) the latero-frontal filtering cilia, (ii) the lateral (pumping) cilia and through the non-ciliated zone at the ventral end of the filament. Calculations indicate that the lateral cilia can generate a sufficient pressure change to 'pump' water through the gill filaments. The velocity profile across the filaments indicates that a backflow can occur in the centre of the channel. Normally the latero-frontal cilia would damp out this backflow but in the case when all the cilia are upright, two 'standing' eddies may form at the mouth of the channel, forcing the incoming water to the side.

Animals↗
PubMed1993

Computerised audit for colorectal cancer.

An audit has been performed of cases of colorectal cancer presenting over an 8-year period. The results of 242 patients are discussed with emphasis placed on the process of surgical audit. In particular, the ease of data handling by a computer database system is stressed. The figures produced on age, sex, presentation, diagnosis, treatment and outcome have allowed a more detailed and fruitful discussion of our practice at the monthly audit meeting.

Adult↗
PubMed1988

The propulsion of mucus by cilia.

The presence of cilia on epithelia of the respiratory tract was reported more than 150 yr ago, and the two-layer model of mucus transport was put forward more than 50 yr ago. However, it is only in the last 10 yr or so that the motion of mucus-propelling cilia of the mammalian respiratory system has been adequately described, and fluid dynamic studies have developed far enough to allow descriptions of the mechanisms by which ciliary movement is coupled to mucus transport. In this review, scientific developments on the study of cilia and mucus, and interactions between them, are drawn together to further understanding of mucociliary clearance mechanisms of the respiratory tract. The study of the cilia incorporates a discussion of the internal mechanics and biochemistry of the ciliary axoneme, the physical principles of the beat pattern, and the (weak) metachronal coordination of cilia in the lung. Mucus rheology plays a central role in mucociliary transport with the rheologic properties of the mucus determining the effective functioning of this clearance mechanism. Theoretical models provide information on the mechanical principles of the beat pattern as well as providing reliable estimates of the transport rates. Although airflow is not thought to contribute to mucus transport in the normal state, high frequency ventilation and coughing may make significant contributions.

Animals↗
PubMed1986

Muco-ciliary transport in the lung.

A two-layer Newtonian fluid model for muco-ciliary transport in the lung is developed where the viscosity of the upper mucous layer is very much greater than the viscosity of the lower periciliary layer. Theory is presented for both cases when the cilia penetrate, and do not penetrate, the very viscous mucous layer. Calculations suggest that, in normal circumstances, it is not essential for the cilia to penetrate the mucus to provide positive transport. However, it does suggest that there is a weak optimal penetration depth of the cilia of between 10-20% of the cilium length. In the case of high ciliary inactivity (e.g. 90% inactive), penetration of cilia into the mucus is essential for normal transport rates suggesting the mucociliary system may be deliberately overdesigned to cater for a whole range of pathological circumstances.

Animals↗
PubMed1986

Dermoid cyst: a rare tumour of the appendix.

Dermoid cyst is a rare but well recognised cause of a mass in the abdomen. As a cause of a palpable mass in the right iliac fossa, dermoid and epidermoid cysts of the caecum have hitherto been described. We here report a case of a dermoid cyst arising from the vermiform appendix.

Adult↗
PubMed1983

A model of ovum transport.

A theoretical fluid dynamical model of ovum transport in the oviduct incorporating transport mechanisms due to ciliary activity, muscular activity and an applied pressure drop across the oviduct is developed. Theory suggests that the cilia provide the steady component of ovum transport whereas muscular activity results in highly oscillatory motion. If muscular activity is to provide transport in a pro-uterine direction, a coordinated sequence of muscular activity with a strong pro-uterine bias is needed. Changes in pressure are highest in the narrowest sections. The highly convoluted rugae may allow "leakback" around the ovum so relieving the pressure drop across the ovum in narrower sections of the oviduct.

Animals↗
PubMed1983

Endoscopic review of patients who have had gastric surgery.

Seventy one patients who had had operations on their stomachs over 15 years previously were examined by endoscopy and multiple mucosal biopsy sampling. Sixty six had histologically proved gastritis (56 chronic atrophic gastritis, 10 superficial gastritis), 38 intestinal metaplasia, and 11 epithelial dysplasia. In three cases the epithelial dysplasia was severe (carcinoma in situ). One patient had an infiltrating carcinoma and another, whose biopsy appearances were reported as severe dysplasia, developed a carcinoma of the stomach eight months later. All patients having undergone gastric surgery more than five years previously should be screened endoscopically and any found to have moderate dysplasia subjected to regular endoscopic screening thereafter. Patients with severe dysplasia (carcinoma in situ) should be considered for radical surgery.

Aged↗
PubMed1980

Relationship between primary breast tumor receptor status and patient survival.

For a minimum of 3- months, 250 women who underwent mastectomy for primary breast cancer have been followed up. ER status has had a pronounced effect upon disease-free interval and survival: in patients with node involvement ER-positive (ER+) tumors carry a better prognosis. Of patients with ER-positive primary tumors, 43% underwent objective response to their secondaries for a minimum period of six months. This compares with a response of only 18% for ER-negative (ER-) tumors. In patients who had previously received endocrine therapy and on relapse were treated with cytotoxic chemotherapy, objective response rate to chemotherapy was better in patients in whom the primary tumor had been ER-, but not significantly so.

Adult↗