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Biomedical subjects

J Marshall

Publications and source records attributed to J Marshall.

At least 343 records · Page 19Linked to original sources
PubMed1989

Intestinal mucosal injury is associated with mast cell activation and leukotriene generation during Nippostrongylus-induced inflammation in the rat.

We examined mucosal injury in the jejunum of the rat during infection with the nematode parasite, Nippostrongylus brasiliensis (Nb). Injury was documented morphologically (increase in crypt length with or without villus atrophy) and biochemically (activities of digestive or proliferative enzymes) and related to mast cell activation and leukotriene generation. At day 4 crypt length and thymidine kinase activity were increased; no changes in villus parameters were recorded. No evidence of mast cell activation was found and leukotriene levels in the mucosa were normal. At day 7, the gut was acutely inflamed and edema was present at the tips of the villi. This progressed to enterocyte detachment, resulting in villus atrophy with decreased activities of brush border enzymes. At this stage mucosal histamine was decreased and rat mast cell protease II (RMCP II) was increased in serum, indicating mast cell activation. In addition, mucosal leukotrienes (LTB4, LTC4, LTE4) were present in significant quantities. Following worm expulsion, the villus abnormalities resolved and serum RMCP II returned to normal. However, the crypt hyperplasia persisted. Our results suggest that during Nb infection at least two components of injury can be identified. One component, epithelial injury at the villus tips, may be related to activation of mucosal mast cells.

Animals↗
PubMed1989

Growth characteristics of central and peripheral bovine corneal epithelial cells in vitro.

Primary cultures of pure bovine corneal epithelial sheets, isolated from either central or peripheral areas of the cornea and grown on an extracellular matrix, exhibited major differences in relation to their respective growth characteristics and morphology. After 15 days in culture, cells of peripheral origin covered a 40% greater area and were 2.75 times more numerous than those of central origin. Most peripheral cells were small with a polygonal morphology, whereas central cells varied considerably in both size and shape, although areas consisting of large cells were regularly observed. Differences in the rates of proliferation between central and peripheral corneal epithelial cells were maintained throughout the first and second subcultures. However, the growth rates were considerably lower in second passage cultures of both central and peripheral cells when compared with those of first passage. The growth characteristics of primary cultures of pure epithelial sheets were confirmed by further studies on corneal buttons in culture. Our results in vitro strongly support the concept of a slow but steady physiological movement of increasingly differentiated cells from the periphery of the cornea towards the centre, resulting in a constant renewal of epithelial cells in vivo.

Animals↗
PubMed1989

Sorsby's fundus dystrophy. A light and electron microscopic study.

The light and electron microscopic changes in both eyes of a patient with Sorsby's fundus dystrophy are reported. The most striking finding was a 30-microns thick deposit present within Bruch's membrane that stained positive for lipids. The deposit has several unique features when compared with those found in other retinal dystrophies and in aged eyes. In addition, there was gross loss of the outer retina, the retinal pigment epithelium was discontinuous, and there was atrophy of the choriocapillaris. These findings are discussed in relation to the published clinical observations of other members of this pedigree.

Choroid↗
PubMed1989

Transplantation of retinal pigment epithelium using a pars plana approach.

We describe a pars plana approach for transplantation of autologous retinal pigment epithelial cells from a peripheral chorioretinal biopsy to prepared Bruch's membrane at the posterior pole of the same eye. The technique has potential application in research and could be clinically applicable in the treatment of senile macular degeneration.

Animals↗
PubMed1989

Corneal topography: a new photokeratoscope.

The assessment of the topography of the cornea is an important modality in the management of surgical procedures complicated by astigmatism. Additionally, the outcome of corneal refractive surgery is often best illustrated by photokeratoscopy. Currently available photokeratoscopes suffer from a number of deficiencies that include (i) the lack of topographic detail from the central cornea, (ii) the difficulty in transporting these units, (iii) the cost of such units. A photokeratoscope which addresses these shortcomings is described.

Cornea↗
PubMed1989

Initial clinical experience using a diode laser in the treatment of retinal vascular disease.

A pilot study has been carried out to investigate the clinical use of an infrared diode laser in the treatment of a number of retinal vascular conditions. A hand-held device was employed initially and subsequently a further prototype was developed for use in conjunction with a standard slit lamp microscope. Thirty-three eyes in thirty patients were treated for conditions such as proliferative diabetic retinopathy, exudative retinopathy and branch and central retinal vein thrombosis. Regression of neovascularisation was observed in 13 of 16 eyes (81%) with proliferative diabetic retinopathy and in six of eight eyes (75%) with branch retinal vein occlusion. Four eyes were successfully treated for established or incipient rubeosis iridis following central vein thrombosis. Focal photocoagulation applied to five eyes for diabetic exudative maculopathy resulted in partial resorption of the exudates. These results are presented together with information on the ease of use of the laser and its reliability. The implications of the development of this instrument in the context of its place in ophthalmic therapy are discussed.

Aged↗
PubMed1989

Structural aspects of laser-induced damage and their functional implications.

The mechanisms of laser damage to the retina are described and observations from laboratory studies are correlated with those from clinical exposure of patients. The sight-threatening consequences of laser lesions are listed, and the further implications of haemorrhages at various levels and locations in the retina are reported. This multifaceted and extensive database is used in developing a system for scoring the sight-threatening potential of a given type of laser lesion in a given retinal location.

Animals↗
PubMed1989

Assessment of corneal wound repair in vitro.

The time course for the closure of linear wounds produced in cultured cell monolayers following either mechanical debridement or excimer laser photoablation were compared. Wounds were produced in the central zone of a confluent layer of bovine corneal epithelial cells, keratocytes, or endothelial cells, and the residual area of the wound measured at regular intervals. Differences in the rate of wound closure between cell types were demonstrated. For epithelial cells the rate of resurfacing after mechanical or excimer laser damage was similar; for keratocytes there was a lag period before cell slide began after laser injury, but the subsequent rate of resurfacing was then similar to mechanical wounds; only for endothelial layers was a significantly reduced rate of closure observed after photoablation as compared to mechanical wounding. In this model of wound healing it appears that it is the mechanism of removal of the extracellular matrix formed by endothelial cells that produces the major difference in the rate of wound closure between mechanical injury or photoablation.

Animals↗
PubMed1989

Frequency of food use data and the multidimensionality of diet.

Cancer epidemiologists rely heavily on the frequency of food use technique to assess dietary risk factors. We found that the accepted procedures for arraying individuals along a continuum, based on their positions within distributions of intakes of specific nutrients, simultaneously array them on other dietary characteristics. A unidimensional approach to dietary assessment could confound cancer risk assessments, and the effects could differ for men and women. We found that men consumed more calories and energy-containing nutrients than women, who were more likely to consume larger amounts of vitamins A and C. Dietary variety was similar for men and women, despite compositional differences in diet. Diets of men contained proportionately more meats, grains and nuts, and alcohol. Diets of women contained more fruits, vegetables, and poultry and fish. Among men, we found stronger intercorrelations among energy intake and intakes of fat, fiber, and vitamin C and among fat intake and intakes of fiber and vitamins A and C. Compositional differences in diet across quartiles of nutrient intake were not consistent for men and women, suggesting that the constellation of dietary risk factors may differ for the two sexes. Men in the lowest quartiles of energy, fiber, and vitamin A intakes had the greatest percent contribution of alcohol to the diet. This pattern was not observed for fat intake levels. Measures of dietary patterns may be needed for more accurate descriptions of the associations of cancer risk and diet.

Alcohol Drinking↗
PubMed1989

Corneal repair following keratectomy. A comparison between conventional surgery and laser photoablation.

We have used the fluorescent dye dichlorotriazinyl aminofluorescein (DTAF) to demonstrate corneal remodeling following keratectomy in the rabbit. The dye was applied to the surface of 3.5 mm diameter anterior keratectomy wounds produced by either lamellar dissection or photoablation with an excimer laser (193 nm) to a depth of 15, 50 or 75 microns. Stromal wounds that had been ablated in 12 concentric steps to produce a graded profile with a central depth of 15 or 30 microns were also studied. The repair process was followed for periods of up to 6 months. These results were compared to wounds of similar dimensions in which an intrastromal keratectomy was performed and the anterior stromal surface replaced. Sections examined by fluorescence microscopy showed that connective tissue was deposited beneath the epithelium of all anterior keratectomy wounds irrespective of their mode of induction or depth. The deposition of this new tissue, and an associated thickening of the epithelium over the wound surface, appeared to be complete by 1 month and tended to restore the original surface contour. The synthesis of connective tissue, but not the hyperplasia of the epithelium, was reduced by local steroid treatment. In contrast, an intrastromal keratectomy only stimulated the deposition of small amounts of new connective tissue at the wound junction without as marked a thickening of the overlying epithelium. These observations emphasize the importance of the epithelium in moderating repair after stromal loss, and suggest that remodeling may result in corneal haze and a change in the desired refraction if refractive surgery is attempted by anterior keratectomy.

Animals↗
PubMed1989

The formation of autofluorescent granules in cultured human RPE.

Although the incomplete degradation of phagocytosed outer segment discs is thought to result in the formation of lipofuscin, there has to date been no proof of this concept. We report for the first time that cultured human retinal pigment epithelial (RPE) cells fed daily doses of isolated rod outer segments for periods of up to 3 months were capable of developing intracellular autofluorescent granules whose morphology and fluorescence characteristics were similar to lipofuscin. These autofluorescent granules were observed as early as 2 weeks following daily challenge with rod outer segments and the number of granules increased with the number of challenge doses until the experiment was terminated after 3 months of daily feeding. We also studied the effects of the antioxidant vitamin E and a drug, Centrophenoxine, which has been purported to slow the formation of lipofuscin formation in vivo. Neither of these additives given either with the challenge or subsequently had any effect on the formation of the intracellular granules. In conclusion, the development of these "lipofuscin-like" inclusions in cultured RPE may provide a model with which to study ageing processes and may provide an understanding of the increased lipofuscin accumulation observed in certain retinal pathologies.

Adolescent↗
PubMed1988

Segmented alpha-helical coiled-coil structure of the protein giardin from the Giardia cytoskeleton.

The parasitic flagellate Giardia is the source of a filamentous protein, giardin, which binds to microtubules. The primary sequence of one giardin chain has been decoded from the base sequences of cDNAs isolated by antibody screens of a library constructed in the expression vector lambda gt11. The amino acid sequence favours a continuous alpha-helical fold for the protein without any inserts of a non-helical character. Analysis of apolar residue positions revealed 35 repeating heptads consistent with coiled-coil structure. This conformation relates giardin to the alpha-type fibrous proteins (k-m-e-f class) like tropomyosin and myosin (also found in Giardia). The giardin sequence has a regular series of skip residues like those at certain positions in the rod section of nematode myosin where the internal apolar seam of the coiled coil is shifted on the helix surface. The skips divide the giardin coil into quasi-equivalent structural segments about 4 nm in length, which might be domains for combining with tubulin subunits in the microtubule surface lattice.

Amino Acid Sequence↗
PubMed1988

Single subunits of the GABAA receptor form ion channels with properties of the native receptor.

The alpha and beta subunits of the gamma-aminobutyric acidA (GABAA) receptor were expressed individually in Xenopus oocytes by injection of RNA synthesized from their cloned DNAs. GABA-sensitive chloride channels were detected several days after injection with any one of three different alpha RNAs (alpha 1, alpha 2, and alpha 3) or with beta RNA. The channels induced by each of the alpha-subunit RNAs were indistinguishable, they had multiple conductance levels (10, 19, 28, and 42 picosiemens), and their activity was potentiated by pentobarbital and inhibited by picrotoxin. The beta channels usually expressed poorly but showed similar single channel conductance levels (10, 18, 27, and 40 picosiemens), potentiation by pentobarbital and inhibition by picrotoxin. The finding that both alpha and beta subunits, examined separately, form GABA-sensitive ion channels with permeation properties and regulatory sites characteristic of the native receptor suggests that the amino acid sequences that confer these properties are within the homologous domains shared by the subunits.

Animals↗