Search PubMed⌕ Search

Biomedical subjects

J Marshall

Publications and source records attributed to J Marshall.

At least 379 records · Page 21Linked to original sources
PubMed1988

A microsystem to assay lysosomal enzyme activities in cultured retinal pigment epithelial cells.

A microsystem to assay the activity of lysosomal enzymes in a small number of cultured RPE cells is described. The activities of acid phosphatase, a-mannosidase, B-glucuronidase and N-acetyl-B-glucosaminidase were estimated in different human RPE cultures of varying passages. Some biochemical characteristics for each of the enzyme assays were studied including the effect of pH, the saturating concentrations of the appropriate substrates and the relationship between the enzyme activity and the number of cells assayed. The method presented is straightforward, avoids complicated tissue fractionation procedures and is able to estimate enzyme activities in as few as 10(4) cells.

Cells, Cultured↗
PubMed1988

Effects of vitreous from photocoagulated eyes on retinal microvascular cells in culture: a preliminary report.

Panretinal photocoagulation was carried out in mini pigs in an attempt to elucidate the mechanisms involved in laser therapy. The effect of the vitreous from these eyes on the proliferation of retinal microvascular endothelial cells was then studied. Vitreous removed 4 days after panretinal photocoagulation had no effect on the proliferation of bovine retinal microvascular endothelial cells in basal medium but inhibited proliferation in growth medium. Control vitreous was mitogenic for the microvascular cells in basal medium but this effect was not observed in growth medium.

Animals↗
PubMed1988

Abnormal glycosylation of the env-sea oncogene product inhibits its proteolytic cleavage and blocks its transforming ability.

Cells transformed by the avian erythroblastosis virus S13 contain three proteins derived from the v-sea oncogene, gp155, gp70 (a cleavage product of gp155), and p38. It is not clear whether only one or all three of these proteins are required for transformation by S13. S13 transformed erythroblasts and fibroblasts revert to a normal morphology in the presence of the alpha glucosidase-1 inhibitor castanospermine, whereas cells transformed by the v-src or v-erbB oncogenes are unaffected by this drug. Treatment with castanospermine does not alter the tyrosine kinase autophosphorylation activity of any of the v-sea products, and the synthesis and processing of p38 is unaffected. Castanospermine modifies the structure of the carbohydrate chains of gp155 such that the glucose residues are retained, thereby inhibiting complex chain formation. Analysis of revertant S13 transformed cells shows that the proteolytic cleavage of the modified form of gp155 is inhibited, resulting in a very low yield of a modified form of gp70. There is no detectable effect of castanospermine on the transport of v-sea gene products to the cell surface. However, due to the inhibition of proteolytic cleavage, the modified form of gp155 is now the major v-sea encoded protein expressed on the cell surface. Thus it appears that the cell surface expression of a v-sea encoded protein with tyrosine kinase autophosphorylating activity is insufficient for cell transformation.

Alkaloids↗
PubMed1988

If I had a stroke.

Explore the source record for details and available documents.

Cerebrovascular Disorders↗
PubMed1988

Hypomagnesemia-induced cardiomyopathy.

Magnesium is the fourth most abundant cation in the body and the second most plentiful intracellularly. Magnesium is crucial to mitochondrial integrity, oxidative phosphorylation, protein synthesis, nucleic acid stability, membrane permeability, and neuro-muscular excitability. In addition, magnesium deficiency induces other electrolyte disturbances including hypocalcemia, hypokalemia, and hypophosphatemia. Because it is not routinely measured, many physicians fail to remember the significance of this element. Reported here is a patient with bulimia who presented with a magnesium deficiency which resulted in her refractory and eventually fatal cardiomyopathy. The cardiac pathophysiology of hypomagnesemia, hypokalemia, hypocalcemia and hypophosphatemia is reviewed and correlated with the clinical and pathological findings.

Adult↗
PubMed1987

Ultrastructural comparison of conventional surgical and argon fluoride excimer laser keratectomy.

We used scanning electron microscopy to examine the structure of the surfaces created during keratectomy procedures carried out by conventional surgery and ablation by an excimer laser. The walls and the floor of the surgical site were rough with undulations greater than 10 micron in size, caused by broken lamellae and ruptured cells. In contrast, the surfaces produced by the excimer laser were smooth with perturbations of 1 micron or less and were sealed with a pseudomembrane. This smooth, sealed surface produced by the laser is probably responsible for the transparency of the healed cornea in contrast to the scarring produced when a conventional surgical keratotomy heals.

Argon↗
PubMed1987

Intraocular argon laser photocoagulation.

Intraoperative photocoagulation using an endolaser delivery system is an important recent development in the field of vitreous microsurgery. Endolaser photocoagulation is indicated in a wide variety of vitreoretinal disorders and offers important advantages over previous techniques of endophotocoagulation using xenon energy. We review our experiences of argon laser endophotocoagulation to identify the role of this technique, the potential hazards and stringent precautions required for theatre personnel.

Animals↗
PubMed1987

The ageing retina: physiology or pathology.

The human retina is a unique component of the nervous system in that throughout life it is continuously exposed to optical radiation between 400 and 1400 nm. The physiology of the ageing retina and the regression in visual performance with age cannot therefore be studied in isolation, or discriminated, from the life long cumulative effects of radiant exposure. This paper describes the spectrum of age related changes in the retina as they merge imperceptibly between declining visual function and overt pathology.

Adolescent↗
PubMed1987

Rise in plasma beta-endorphin, ACTH, and cortisol in cancer patients undergoing whole body hyperthermia.

It has been previously reported that sauna-induced fevers (approximately 39 degrees C) result in rises of beta-endorphins in normal volunteers. This report describes changes in plasma beta-endorphins in cancer patients undergoing whole body hyperthermia (40.5 degrees C to 41.8 degrees C). Results presented show that there is a linear relationship between thermal stress, defined in terms of core temperature and/or duration of hyperthermia, and the quantitative rise in plasma beta-endorphin levels. Data relating to changes in ACTH and cortisol levels are in a single temperature range (41.5 degrees C--41.8 degrees C) are also reported.

Adolescent↗
PubMed1987

The reliability of dietary history from the distant past.

A major barrier to the conduct and interpretation of retrospective studies of diet and cancer has been uncertainty about the reliability of retrospective measures of diet from the distant past. The authors therefore conducted a study to assess the reliability of retrospective dietary reports and to determine whether the retrospective report or the report of current diet is the better indicator of past diet. Persons (n = 323) originally interviewed regarding their diets in 1975-1979 were retrospectively reinterviewed in 1984-1985. There was little difference between the retrospective reports and the reports of current diet when group means were examined as indicators of past diet. The retrospective reports tended to overestimate the past frequency of consumption for most foods, whereas the reports of current diet tended to yield underestimates. Because food frequency-based dietary history data are more useful for ranking study subjects than for generating estimates of group means, correlation analysis was used as the principal assessment of the reliability of the two indicators of past diet. The retrospective reports more closely correlated with the diet reported at the original interview than did the report of current diet (for 37 of 47 foods). Nutrient indices based on the retrospective history were also more highly correlated with those of the original diet than were indices based on the current diet. No differences were noted in the reliability of retrospective reports according to age or sex. Subjects accurately reported perceptions of changes in their consumption of most foods, yet an estimate of past diet created by adjusting current diet for perceived change did not correlate more highly with the original diet than did the retrospective report. The authors conclude that assessing current diet to make inference about diet from the distant past does not yield more reliable estimates of past diet than does the retrospective dietary history. The best estimate of diet from several years in the past may be derived directly from a retrospective dietary history which focuses on that past period of time.

Aged↗
PubMed1987

The cutaneous microbiology of normal human feet.

A survey has been made of the bacterial and fungal populations carried at three different sites on the feet of 60 individuals. The bacteria found at the three sites were quantitatively similar and Micrococcaceae and aerobic coryneform bacteria predominated. The carriage of other bacterial groups was generally low. There was a quantitative variation between sites--mean total counts were 1.04 X 10(7) cfu/cm2 skin in the fourth toe cleft, 4.08 X 10(5) cfu/cm2 skin on the sole and 1.21 X 10(3) cfu/cm2 skin on the dorsal surface. Staphylococci were most often dominant on the sole and dorsal surface whereas aerobic coryneforms predominated in the majority of fourth toe clefts. The higher the total count at a given site the more likely it was that aerobic coryneform bacteria predominated. The skin surface pH was significantly higher on the sole (mean value 6.25) than on the dorsal surface (mean value 5.23). Factors controlling the microbial ecology of the foot are discussed.

Actinomycetales↗
PubMed1987

Clinical approach to the aged brain.

There are two main clinical manifestations of the aging brain, which appear to be independent of any disease process, namely adaptability and general slowing. Impaired adaptability depends in part on poor function of the homeostatic mechanisms. General slowing affects all levels of nervous activity and can be measured in various ways. Research relevant to the clinical problem is reviewed and evaluated.

Aging↗