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Biomedical subjects

N J Watson

Publications and source records attributed to N J Watson.

15 recordsLinked to original sources
PubMed2006

An observational case study of ozone and precursors inflow to South East England during an anticyclone.

Summertime photochemical air pollution episodes within the United Kingdom have been proposed via modelling studies to be strongly influenced by regional scale inflow of air from the continental European boundary layer. We present a vertically resolved case study using measurements made from the NERC/Met Office BAe 146 research aircraft on 18th August 2005 over the South East of England and the North Sea during a weak anticyclone centred over Northern Europe. The vertical distribution of ozone, CO, NO(x), peroxyacetyl nitrate (PAN) and a wide range of both nonmethane hydrocarbons (NMHC) and oxygenated volatile organic compounds (OVOCs) were determined between 500 ft (approximately 152 m) and 7000 ft (approximately 2134 m) over the East Anglia coastline and 50 km inland. In excess of 80 ppbV ozone was observed within inflowing boundary layer air over the North Sea coast in a broad N-S sloping feature around 60 km wide. The inflowing feature of European origin was also observed further inland within the boundary layer albeit with lower, more variable, ozone mixing ratios. The increased variability in ozone over land was a product of titration by fresh surface emissions of NO via rapid upward transport in thermals, a hypothesis supported by the observed vertical wind speed component. Fast boundary layer mixing over land was further illustrated by a uniform distribution in reactive alkenes. A comparison between aircraft and surface O(3) UK AUN (Automatic Urban Network) measurements showed good agreement with the inland site, Sibton, but marked differences with the coastal monitoring site at Weybourne, potentially due to gradients established by ocean deposition in stably stratified marine air.

Air Pollutants↗
PubMed1993

Corneal epithelial cell migration in humans: 'hurricane and blizzard keratopathy'.

Replicative turnover of the corneal epithelium is believed to occur from a population of stem cells located at the corneo-scleral limbus. During the healing of corneal epithelial wounds, sheets of epithelial cells move centripetally from the limbus and circumferentially along the limbus to cover the defect. A whorled or vortex pattern, similar to that seen in cornea verticillata, has been reported to occur on the corneal surface as an effect of topical steroid medication, during the healing of grafted corneas. This condition has been termed 'hurricane keratopathy'. We have noted this appearance in 6 patients who did not have corneal grafts. In all our patients the whorled pattern was best visible on fluorescein staining. This feature differentiates 'hurricane keratopathy' from cornea verticillata secondary to deposition of substances in corneal epithelial cells. Further, in all our patients the vortex was clockwise. Examination of illustrations of 'hurricane keratopathy' and cornea verticillata reported in the literature reveals that the whorled pattern is almost always clockwise. We believe that this specific pattern is likely to be due to the effect of the electromagnetic fields of the eye on the migrating epithelial cells and present a theory to explain this phenomenon. In 3 eyes of 2 other patients with chronic epitheliopathies we observed a random distribution of cells that did not conform to any specific pattern. We have termed this condition 'blizzard keratopathy'.

Adult↗
PubMed1993

A spectrum of clinical signs in anterior uveitis.

The range of clinical changes that occur in posterior uveitis have been well documented. We describe two clinical features of anterior uveitis which we have termed 'iris pigment epithelitis' and 'iris vasculitis'. Other clinical forms of iritis also exist and together with our described findings parallel the spectrum of clinical presentations in posterior uveitis.

Adult↗
PubMed1992

Echographic diagnosis of advanced Coats' disease.

Standardised echography was utilised to diagnose two cases of advanced Coats' disease. The characteristic acoustic features included extensive, poorly mobile retinal detachment; dense, dispersed subretinal opacities; looping of peripheral retina and absence of solid mass lesion and calcification. As enucleation of two eyes was necessary, it has proved possible to correlate the echographic and histological findings of this disease. The echographic features of other common causes of leukocoria are also discussed.

Electroretinography↗
PubMed1992

Anterior segment ischemia.

I present, to my knowledge for the first time, a case of anterior segment ischemia following a trabeculectomy performed under anesthetic.

Aged↗
PubMed1991

The oval pupil.

The dynamics of pupillary dilation induced by Phenylephrine 10% and Cyclopentolate 1% have been examined by flash photography. A correlation between anterior chamber depth and the pupil shape on dilation with Phenylephrine Hydrochloride 10% is described. It is postulated that these pupillary dilation dynamics support a sympathetic abnormality as a trigger for acute primary angle closure glaucoma.

Adolescent↗
PubMed1991

A case of sinusitis presenting with spheno-cavernous syndrome: discussion of the differential diagnosis.

A 60 year old gentleman presented with a left spheno-cavernous syndrome resulting in impaired ocular motility, proptosis and visual loss in an otherwise clinically quiet eye. The history led to a clinical suspicion of posterior ethmoiditis, which was confirmed on C.T. scanning. Surgical drainage and antibiotic treatment resolved the symptoms, but visual impairment persisted. The differential diagnosis and management of spheno-cavernous syndrome is discussed in context with this atypical presentation of orbital cellulitis.

Combined Modality Therapy↗
PubMed1984

The role of sodium citrate in the dysfibrinogenaemia of liver disease.

The addition of excess sodium citrate to plasma was found to inhibit fibrin polymerisation (clot opacity) from patients with cirrhosis, hepatitis and hepatoma but not from normal controls. Abnormal clot opacity in plasma from patients with liver disease could be partly or completely abolished by removal of citrate ions by dialysis against citrate-free buffer, but not by dialysis against buffer containing citrate. Similar results were observed in plasma freed of calcium ions by treatment with EGTA. Treatment of plasma with neuraminidase largely abolished the inhibitory effect of excess citrate, and the thrombin times and clot opacity of asialofibrinogen were less affected by citrate than native fibrinogen. In addition, the effects of citrate on the clotting of purified, calcium-free fibrinogen from cirrhotic patients correlated with the sialic acid content. It is concluded that binding of citrate ions to fibrinogen renders the molecule acutely more sensitive to elevations in the sialic acid content, and that a simple plasma clot opacity test in the presence of excess citrate may be a useful aid in the differential diagnosis of liver disease. These findings may also explain why defects in fibrin polymerisation observed in plasma are not always reproduced in purified fibrinogen or fibrin monomer preparations.

Afibrinogenemia↗