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Biomedical subjects

N J Young

Publications and source records attributed to N J Young.

8 recordsLinked to original sources
PubMed1994

Usefulness of magnetic resonance imaging for evaluating great-vessel anatomy after arterial switch operation for D-transposition of the great arteries.

Magnetic resonance imaging (MRI) produces high-resolution images of great-vessel anatomy in pediatric patients. In this study seven patients, aged 6 to 27 months were evaluated by using gated MRI and two-dimensional echocardiography 4 to 26 months after arterial switch operation for D-transposition of the great arteries. Measurements were taken at the right and left ventricular outflow tracts, beneath the semilunar valves, at the midaortic sinuses, at the anastomotic sites of the main pulmonary artery and the aorta, at the origin of the branch pulmonary arteries, and at the distal pulmonary arteries 1 cm beyond the bifurcation. Concordant results were obtained with both imaging techniques from all sides with the exception of the left pulmonary artery and the right pulmonary artery. With MRI, four patients had significant narrowing at the right pulmonary artery origin and six patients had narrowing at the left pulmonary artery origin. With two-dimensional echocardiogram, two patients had narrowing at the right pulmonary artery origin and four patients had narrowing at the left pulmonary artery origin. The measured pulmonary artery intraluminal diameters in these patients were consistently smaller when assessed by MRI versus two-dimensional echocardiography. To verify these results, five of seven patients underwent cardiac catheterization to provide physiologic correlation before reoperation; the MRI results were found to be significantly closer to the actual catheterization measurements. We conclude that MRI is a sensitive imaging technique for evaluation of great-vessel anatomy in patients after arterial switch operation for D-transposition of the great arteries. It is particularly useful in the evaluation of the branch pulmonary artery anatomy.

Aorta↗
PubMed1992

Progesterone metabolism in vitro in the decapod crustacean, Penaeus monodon.

Thin-layer chromatography (TLC) and reversed-phase high-performance liquid chromatography (RP-HPLC) with on-line detection of radioactive steroids were applied to identify metabolites of [4-14C]progesterone incubated in vitro with prawn ovary. There was extensive metabolism of progesterone by stage II (vitellogenic) ovary of Penaeus monodon. The most abundant metabolites were 5 alpha-pregnane derivatives together with two minor metabolites, 20 alpha-hydroxypregn-4-en-3-one and 1,4-pregnadiene-3,20-dione. In contrast, a much lower level of progesterone metabolism was observed in stage 0 (immature) ovary of this species. The hepatopancreas, gill, and abdominal muscle of P. monodon all metabolised [4-14C]progesterone to varying degrees, generating materials similar to those produced by the ovary. A comparative study of progesterone metabolism in stage II ovary of Nephrops norvegicus indicated that one metabolite, 20 alpha-hydroxypregn-4-en-3-one, was produced.

Abdominal Muscles↗
PubMed1991

Identification of free and conjugated ecdysteroids in cercariae of the schistosome Trichobilharzia ocellata.

Extracts of cercariae of the avian schistosome Trichobilharzia ocellata were analysed for the presence of ecdysteroids by radioimmunoassay, high-performance liquid chromatography monitoring fractions by radioimmunoassay, and gas chromatography/mass spectrometry (selected ion monitoring). Both free ecdysteroids and polar conjugated ecdysteroids were detected in the cercarial extracts. The free ecdysteroid fraction, as well as the hydrolysed polar conjugated ecdysteroid fraction, contained both ecdysone and 20-hydroxyecdysone in approximately equal amounts. The amount of ecdysteroids detected is comparable to those found in other platyhelminths. A possible role for the ecdysteroids in the development of the parasite and/or the interactions between the parasite and its intermediate host, the freshwater snail Lymnaea stagnalis, is discussed.

Animals↗
PubMed1985

A new directly moulded patellar-tendon-bearing socket.

Silicone rubbers and casting tapes individually have previously been used in the manufacture of sockets (Swanson, 1972; Sweitzer, 1973; Ruder, 1977; Graves, 1980; Aqualite, 1982). The authors believe that the present combination of these materials to manufacture a directly moulded socket with a complete silicone rubber lining of variable thickness has not previously been described. The new socket, after addition of the modular components, allows fitting of an aligned below-knee prosthesis within three hours. The socket (Fig. 1.) is made directly on the below-knee stump, can be completed with experience in an hour and does not require the use of specialized equipment. The socket consists of an outer supportive Scotchflex layer inside which is a lining of soft smooth biocompatible silicone rubber of deliberately variable thickness to allow pressure tolerant areas to accept more load and pressure sensitive areas to accept less load (Fig.2). The thicker areas of silicone are produced by applying carefully cut Plastazote pads to the pressure sensitive areas. The thickness and extent of the pads is individually assessed according to the estimated sensitivity of the particular area (Fig. 3). The Scotchflex socket is then manufactured directly on the below-knee stump with these pads applied. The pads are then removed prior to insertion of a semi-liquid silicone rubber. Thus, when the socket with the liquid silicone rubber is re-applied to the stump, the space produced by the pads is filled by the rubber which then sets at room temperature. In this way a layer of variable thickness is produced.(ABSTRACT TRUNCATED AT 250 WORDS)

Artificial Limbs↗
PubMed1984

A method for socket duplication using Silcoset R 105.

A technique for duplicating an existing comfortable socket has been in use for two years. The method, using Silcoset R 105, provides the prosthetist with a re-usable positive mould thus enabling the manufacture of two prostheses of comparable fit.

Artificial Limbs↗
PubMed1980

PIgment epithelial diseases with abnormal choroidal perfusion.

Sixteen patients, seen during the first week of their disease, had swelling of the retinal pigment epithelium and angiographic evidence of a widespread abnormality of choroidal filling. The patients fell into three groups: In Group 1 there were multifocal pigment epithelial lesions identical to those of acute posterior multifocal placoid pigment epitheliopathy. In Group 2 the pigment epithelial lesions were confluent. The retina was not detached in either of the these groups. In Group 3, multifocal lesions of the pigment epithelium were associated with retinal detachment. We postulated that all patients had diffuse choroidal hypoperfusion and focal pigment epithelial infarct which, in turn, may have been caused by a variety of basic disorders. We detected no relevant systemic abnormalities in any of the patients.

Adolescent↗
PubMed1978

Bilateral acute retinal necrosis.

In this paper 4 patients are described who had bilateral symmetrical confluent retinal swelling followed by apparent necrosis and sloughing of the retina into the vitreous. The disease was accompanied by signs of uveitis and the clinical appearance suggested inflammation rather than infarction as the pathogenic mechanism. No systemic abnormalities were found by which the aetiology could be identified.

Acute Disease↗