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Biomedical subjects

J Marshall

Publications and source records attributed to J Marshall.

At least 415 records · Page 23Linked to original sources
PubMed1986

A comparative study of corneal incisions induced by diamond and steel knives and two ultraviolet radiations from an excimer laser.

This paper reviews the potential role of excimer lasers in corneal surgery. The morphology of incisions induced by two wavelengths of excimer laser radiation, 193 nm and 248 nm, are compared with the morphology of incisions produced by diamond and steel knives. Analysis suggests that ablation induced by excimer laser results from highly localised photochemical reactions and that 193 nm is the optimal wavelength for surgery. The only significant complication of laser surgery is loss of endothelial cells when incisions are within 40 micron of Descemet's membrane.

Animals↗
PubMed1986

Immunocytochemical differentiation of microtubules in the cytoskeleton of Giardia lamblia using monoclonal antibodies to alpha-tubulin and polyclonal antibodies to associated low molecular weight proteins.

In interphase trophozoites of Giardia lamblia, separate populations of microtubules constitute the four parts of the mastigont apparatus: flagella, ventral disc, funis and median body. Antigenic differences between the tubules have been investigated by light and electron immunocytochemistry after labelling with two monoclonal antibodies to alpha-tubulin (YL 1/2 and YOL 1/34 clones), and with polyclonal antibodies to Giardia tubule-associated proteins. Both anti-tubulins stained all tubules after isolated structures were fixed in formaldehyde, but different patterns of reactivity were shown by unfixed tubules. YL 1/2 antibodies labelled flagellar axonemes and basal bodies, funis and median body tubules. Disc microtubules were mostly unlabelled, but the antibody bound strongly to the outer edge of the disc where the ends of tubules are embedded. YOL 1/34 antibodies stained disc tubules uniformly, and cross-reacted with the median body but not with tubules of axonemes, basal bodies or funis. Antibodies to giardins 14A and 14B (approximately 30 000 Mr filament-forming proteins) localized these proteins in the microribbons attached to disc microtubules. The median body was also labelled by anti-giardins, indicating an ontogenetic relationship between this organelle and the ventral disc. A second set of approximately 30 000 Mr proteins with no immunoreactivity to anti-giardin was found in flagella purified without removing flagellar membranes. These polypeptides were Triton-soluble and therefore probably originated from an extra-axonemal site. A rabbit antiserum to the labile flagellar proteins specifically stained the two ventral flagella, but not the other six flagella on this cell.

Animals↗
PubMed1986

Magnetic resonance imaging of thoracic aortic aneurysms: comparison with other imaging methods.

Fifteen patients with thoracic aortic aneurysms had magnetic resonance images (MRI) and at least one additional diagnostic image study: thoracic aortography, computed tomography (CT), or two-dimensional echocardiography. Twenty aneurysms were demonstrated by MRI, 19 by the other studies. One small saccular aneurysm was missed by CT. There was complete agreement between MRI and other studies regarding aneurysm morphology, and good correlation in diameter measurements of the aneurysms and at multiple additional aortic levels.

Adolescent↗
PubMed1986

Structured postoperative teaching and knowledge and compliance of patients who had coronary artery bypass surgery.

A convenience sample of two comparable groups of patients who had coronary artery bypass surgery was studied to assess the effectiveness of a structured teaching guide used by nurses in educating the patient and his family about normal postoperative recovery. Preoperative health assessments were performed on 64 patients, and risk factors for heart disease were identified for each individual. One group was educated by an unstructured method; the other group received structured teaching with the use of a guide developed by nurses experienced in recovery after open heart surgery. Knowledge was assessed before instituting teaching and on discharge from the hospital. All patients were again assessed 6 weeks after discharge for postoperative health and compliance with their health risk factors identified earlier. An analysis of variance with repeated measures revealed that both groups had higher total knowledge scores after surgery. Most postoperative health behaviors (angina, smoking, hypertension, and diet) were comparable between groups. However, those patients who had structured postoperative teaching walked more blocks after surgery (mean = 15.61) than those patients who received routine teaching (mean = 7.00) (p less than 0.005), although these two groups were not equivalent before surgery. In addition, the patients who had structured teaching had higher total compliance scores (mean = 86.8) than those who had unstructured teaching (mean = 79.5) (p less than 0.05). Therefore although structured teaching may not have initially affected patient's knowledge, it may have had an impact on their compliance with postoperative health behaviors.

Aged↗
PubMed1985

Identification and characterization of the chicken transferrin receptor.

Among a panel of monoclonal antibodies that recognize chicken haematopoietic-differentiation antigens, one, JS 8, was found to immunoprecipitate a 95000-Mr cell-surface protein from chicken erythroblasts transformed with avian-erythroblastosis virus. This protein was shown, by affinity chromatography on immobilized chicken transferrin (conalbumin), to be the chicken transferrin receptor. Although immunologically unrelated to the human transferrin receptor, biochemical comparison of the chicken transferrin receptor to the human receptor showed similarities with respect to the pattern of biosynthesis, degree of glycosylation, dimerization in the absence of reducing agents and subcellular localization. The present report contrasts with recent ones describing the chicken transferrin receptor isolated from embryonic tissues as a 58000-Mr protein.

Animals↗
PubMed1985

Prolonged outbreak of Norwalk gastroenteritis in an isolated guest house.

During November and December 1982, a persistent outbreak of gastroenteritis took place in an isolated guest house. An estimated 26% of the changing population of guests and staff developed symptoms. Laboratory studies implicated Norwalk agent as the cause of illness, although the original source of the outbreak could not be established. Information on clinical features of the illness, its mode of spread, and eventual control is presented.

Adolescent↗
PubMed1985

Regulation of cerebral blood flow in response to changes in blood viscosity.

Cerebral blood flow (CBF) was measured by the non-invasive xenon-133 technique in patients with increased blood viscosity as a result of paraproteinaemia or leukaemia. A highly significant inverse relation was found between CBF and arterial oxygen content in 59 paraproteinaemic patients. There was no significant correlation between CBF and whole blood viscosity, and no significant difference between CBF in paraproteinaemic patients and a matched group of anaemic patients. 7 leukaemic patients with up to threefold increases in whole blood viscosity were also found to have CBF appropriate to their degree of anaemia. The effects of treatment to reduce blood viscosity were studied in 7 paraproteinaemic and 5 leukaemic patients; changes in CBF were significantly related to changes in arterial oxygen content but not to changes in blood viscosity. These studies confirm the importance of arterial oxygen content in the determination of CBF, and demonstrate that regulatory mechanisms can maintain normal cerebral oxygen transport despite increased plasma and whole blood viscosity.

Adult↗
PubMed1985

Population pharmacokinetics of racemic warfarin in adult patients.

The population pharmacokinetics of racemic warfarin was evaluated using 613 measured warfarin plasma concentrations from 32 adult hospitalized patients and 131 adult outpatients. Warfarin concentrations were measured in duplicate using a high-performance liquid chromatographic procedure. The pharmacokinetic model used was a one-compartment open model with first-order absorption (absorption rate constant set equal to 47 day-1) and first-order elimination. The extent of availability was assumed to be one. A linear regression model was used to evaluate the influence of various demographic factors on warfarin oral clearance. Age appeared to be an important determinant of warfarin clearance in this adult population. There was about a 1%/year decrease in oral clearance over the age range of 20-70 years. Smoking appeared to result in a 10% increase in warfarin clearance, while coadministration of the inducers phenytoin or phenobarbital yielded about a 30% increase in clearance. This study has yielded a predictive model that, when combined with appropriate pharmacological response data, may be useful in the design and adjustment of warfarin regimens.

Adolescent↗
PubMed1985

Repigmentation of human retinal pigment epithelial cells in vitro.

Cultured human retinal pigment epithelial (RPE) cells readily ingested both melanin and lipofuscin isolated from human RPE cells. Up to 7 days post-challenge ingested granules demonstrated no evidence of lysis or aggregation within secondary lysosomes. When cultures containing ingested melanin and lipofuscin were subcultured the cells gradually depigmented due to a redistribution of pigment granules amongst daughter cells. Quantitative analysis demonstrated that the accumulation of both types of granule was linear over a 24 hr challenge period. This study reports a technique of 'artificially' repigmenting cultured human RPE cells and thus offers the potential for in vitro investigations of the role of these inclusions in various dynamic aspects of cellular metabolism.

Adult↗
PubMed1985

Pregnant and pseudopregnant mice produce a low cytotoxic alloantibody response when challenged by fetal but not adult F1 alloantigens.

The tertiary cytotoxic alloantibody response of syngeneically pregnant, pseudopregnant and non-pregnant BALB/c mice immunised with semi-allogeneic lymphocytes from fetal and adult (CBA X BALB/c)F1 donors was investigated by the microcytotoxicity method. The pregnant and pseudopregnant animals showed a significantly lower response to fetal alloantigens compared to that towards adult alloantigens (P less than 0.001). In contrast, control non-pregnant recipients showed no diminution of response to fetal alloantigens. These observations suggest that the hormonal status of pregnancy, even in the absence of a conceptus, permits a low cytotoxicity antibody response when challenged specifically by fetal, but not when challenged by adult, F1 alloantigens.

Animals↗
PubMed1985

An ultrastructural study of corneal incisions induced by an excimer laser at 193 nm.

Far ultraviolet light (193 nm) produced by an excimer laser has been used to produce a variety of incisions in the corneas of anaesthetised rabbits. Tissue was lost from the site of irradiation but the nature of the underlying molecular interactions responsible for such tissue erosion remain obscure. Ultrastructural analysis of the walls of the ablated areas show damage to the adjacent structures to be confined to a zone 60 to 200 nm in width. These dimensions could either be attributed to photochemical processes in which high energy photons directly break organic molecular bond, or to thermal reactions which result in limited heat flow and damage confined to the absorption depth at 193 nm of less than 1 micron. In non-penetrating incisions that reached within 40 micron of Descemet's membrane, endothelial cells were lost beneath the line of the irradiation. This spalling of cells seemed to be generated by shock or acoustic waves.

Animals↗
PubMed1985

Lactation and breast cancer. Evidence for a negative association in premenopausal women.

The authors report a case-control study of breast cancer based on an analysis of data collected by interview between the years 1957-1965 from women residing in the communities of Buffalo and Kenmore, New York. Prior reproductive factors, including a detailed lactation history, were examined for 453 white females with breast cancer and 1,365 white females without breast cancer who were selected randomly from the population of Buffalo and Kenmore. There is evidence of a negative association between length of nursing and breast cancer risk in premenopausal women which is not seen in the postmenopausal women. This apparent "protective" effect of lactation persists after statistical control for the potential confounding factors of age, parity, age at first pregnancy, age at menarche, and education. Cases are more likely than controls to have reported unsuccessful lactations due to "insufficient milk." The findings of this study, in conjunction with the authors' review of previously published studies that have examined prior lactation as related to breast cancer risk, suggest that there may be an independent negative association between nursing and subsequent breast cancer risk in premenopausal women. Whether this means that breast feeding is protective or that some women who are unsuccessful at lactation are at increased risk for subsequent breast cancer is not clear. A detailed reanalysis of existing data and more careful attention to detailed prior breast function/dysfunction in future studies are recommended.

Adolescent↗