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Biomedical subjects

M O'Brien

Publications and source records attributed to M O'Brien.

At least 271 records · Page 15Linked to original sources
PubMed1984

Simultaneous demonstration of membrane antigens and cytochemistry at ultrastructural level: a study with the immunogold method, acid phosphatase and myeloperoxidase.

We describe a method for electron microscopy that combines myeloperoxidase or acid phosphatase cytochemistry with the labelling of cell surface antigens with monoclonal antibodies and colloidal gold. This technique was tested in samples of normal mononuclear cells, leukaemic T cells with a mature or immature phenotype and an acute myeloid leukaemia. This method allows the demonstration at a single cell level of ultrastructural morphology, cytochemical reaction and the presence of a membrane antigen. It will improve further the analytic power of electron microscopy in the characterization of leukaemic cells particularly in cases of mixed leukaemias and in the study of normal haemopoietic differentiation with monoclonal antibodies.

Acid Phosphatase↗
PubMed1983

Ultrastructural cytochemistry of chronic T-cell leukaemias. A study with four acid hydrolases.

The ultrastructural localization of four acid hydrolases (acid phosphatase, beta-glucuronidase, beta-glucosaminidase and alpha-naphthylacetate esterase) has been studied in lymphocytes from 16 patients with three types of chronic T-cell leukaemia, namely, T-prolymphocytic leukaemia (T-PLL), T-chronic lymphocytic leukaemia (T-CLL) and adult T-cell lymphoma leukaemia (ATLL). Different patterns of enzyme distribution were observed in the leukaemic T-cells from these disorders. In T-PLL, reactivity for the four acid hydrolases was confined to single or a few large granules. Gall bodies were reactive for beta-glucuronidase, b-glucosaminidase and alpha-naphthylacetate esterase but apparently unreactive for acid phosphatase. In T-CLL, scattered small- to medium-size cytoplasmic granules and many parallel tubular arrays were strongly reactive for acid phosphatase, beta-glucuronidase and beta-glucosidase but showed no reactivity for alpha-naphthylacetate esterase. Intermediate features were observed in ATLL. The observed differences in enzyme reactivity reflect a different content of lysosomal granules in the various types of leukaemic T-cells. They also suggest that similar differences may be found in normal T-lymphocyte subsets.

Acid Phosphatase↗
PubMed1983

Hypolipidemic effects of clofibrate and selected chroman analogs in fasted rats: II. High sucrose-fed animals.

The hypolipidemic properties of ethyl 6-chlorochroman-2-carboxylate (II), 6-phenylchroman-2-carboxylate (III) and 6-cyclohexylchroman-2-carboxylate (IV) were compared to clofibrate (I) in sucrose-fed fasted male Sprague-Dawley rats. All compounds were administered at doses of 0.2 and 0.4 mmol/kg, orally, twice daily for 7 consecutive days. In this model, II was a more effective hypocholesterolemic drug than clofibrate, whereas III and IV were inactive. Chlorochroman II, like clofibrate, decreased serum alpha-lipoprotein cholesterol and pre-beta-lipoprotein triglyceride concentrations and concomitantly increased serum beta-lipoprotein triglyceride concentrations. In clofibrate-treated rats, serum free cholesterol concentrations increased concurrent with a reduction in serum lecithin: cholesterol acyltransferase activity, but no such correlation was observed for II. Only II lowered liver cholesterol levels and increased liver triglyceride levels. No consistent inhibition of liver microsomal 3-hydroxy-3-methylglutaryl-CoA reductase activity was observed with these analogs. The observed changes in triglyceride and cholesterol concentrations among serum lipoproteins were of a greater magnitude after chlorochroman II and clofibrate administration to sucrose-fed rats than in our previous studies using chow-fed fasted rats. These data suggest that chloro-substitution at the 6-position of the phenylchroman ring is important for hypolipidemic activity of these cyclic clofibrate analogs.

Animals↗
PubMed1983

A new method for the three-dimensional in vitro growth of human cancer cells.

A method has been developed which allows, for the first time, the in vitro growth of human tumor cells in calcium alginate gel microcapsules. The three-dimensional matrix is permeable to macromolecules of at least 200 000 molecular weight (MW) (e.g., carcinoembryonic antigen) and provides an environment for organized growth and differentiation more comparable to in vivo growth than monolayer culture. This inexpensive, nondestructive procedure allows studies of morphological, biochemical and immunochemical parameters of human tumor cells within a single model.

Adenocarcinoma↗
PubMed1983

Candidate counterparts of Sézary cells and adult T-cell lymphoma-leukaemia cells in normal peripheral blood: an ultrastructural study with the immunogold method and monoclonal antibodies.

The ultrastructural and immunologic features of normal convoluted T-lymphocytes were studied with a panel of monoclonal antibodies and the immunogold technique and these were compared with cells from patients with Sézary syndrome (SS) and adult T-cell lymphoma-leukaemia (ATLL). According to the characteristics of the nucleus, two distinct T-cell subtypes, representing 2-4% of normal peripheral blood lymphocytes were recognized: (i) a cerebriform lymphocyte ('Sézary-like') characterized by narrow and deep nuclear indentations, closely resembling the cells of SS, and (ii) a convoluted or polylobated lymphocyte ('ATLL-like'), with shorter and broader nuclear indentations than those seen in SS, that resemble the cells of ATLL. Both types of lymphocytes were positive with the monoclonal antibodies OKT3, OKT4, OKT17 and FMC3 and were negative with OKT8, OKM1 and FMC4 (anti-HLA-Dr) as SS and ATLL cells. A difference was observed with the expression of the anti-T monoclonal antibody 3Al: Sézary-like lymphocytes, like SS and ATLL cells, were 3Al negative whilst ATLL-like lymphocytes were 3Al positive. The close morphological and membrane phenotype similarities observed between these two types of lymphocytes and the cells from SS and ATLL suggest that they may well represent the normal counterparts of the malignant T cells in both conditions.

Antibodies, Monoclonal↗
PubMed1983

Galactosamine inhibition of protein synthesis in Bacteroides thetaiotaomicron.

Galactosamine does not support growth of Bacteroides thetaiotaomicron. Despite this, galactosamine was more effective than utilizable carbohydrates such as glucose in preventing synthesis of the inducible enzymes alpha-glucosidase and chondroitin lyase. Galactosamine also stopped overall protein synthesis. By contrast glucose and other utilizable carbohydrates increased the rate of protein synthesis. Addition of glucose to bacteria which had been treated with galactosamine restored the ability of the bacteria to synthesize protein and to produce inducible enzymes. Moreover, when B. thetaiotaomicron was incubated with [1-14C]galactosamine for 30 min at 37 degrees C, about one-third of the label which was taken up by the cells comigrated with glucosamine-6-phosphate on a thin-layer chromatogram. Thus galactosamine appears to be phosphorylated by the bacteria. After 2 h incubation of the bacteria with [1-14C]galactosamine, there was a significant increase in the amount of label which could be extracted from acidified extracellular fluid with diethyl ether. This indicates that galactosamine can be metabolized to the level of volatile fatty acids. The rate of uptake of galactosamine and the amount of labeled fatty acids produced from galactosamine were both much lower than the values obtained when glucosamine was the substrate. Thus, although some metabolism of galactosamine occurs, the rate is apparently too slow to enable galactosamine to support growth of B. thetaiotaomicron.

Bacterial Proteins↗
PubMed1983

The effect of two body positions on head righting in severely disabled individuals with cerebral palsy.

This study examines the association between head righting and two commonly used therapeutic positions: semiprone on an inclined prone positioner and upright short-sitting in an adapted wheelchair. The subjects were 26 individuals with cerebral palsy and multiple handicaps who had difficulty maintaining active head control in a vertical orientation. Such head control is necessary for attending to learning tasks in the classroom and activities of daily living in the clinic. The frequency and duration of head righting during a feeding task was measured by means of a mercury switch system mounted on a headband and attached to an electromechanical digit counter and a clock. Measurements of duration and frequency beyond the predetermined range of functional head righting plus measurements on five control variables were analyzed by four statistical methods: t-test on the means, simple correlation, cannonical correlation, and regression analysis. The control variables were age, mobility level, degree of hypertonicity, level of seizure activity, and level of reflex maturity. Results indicate that, in this severely handicapped population, head righting while in the adapted wheelchair is no different from head righting while in the semiprone position. One control variable, level of independent mobility, was positively correlated with the length of time that subjects were able to maintain head righting in the semiprone position.

Adolescent↗
PubMed1983

Maytansine as a cause of acute proliferative disorder of bladder urothelium in the rat.

Male Wistar Lewis rats were injected with maytansine at a total dose of 0.425 to 0.6 mg/kg over a 3-week period. Biopsies taken at 5 weeks showed that 23% of the bladders had hyperplasia or other abnormalities. Of the bladder biopsies done for the first time at 8 weeks, 80% demonstrated papillary hyperplasia. A small number of biopsies at 13 and 19 weeks still showed hyperplasia and minimal inflammatory reaction. These results were seen regardless of prior biopsy, the presence of bladder calculi, and/or the dose level used. It is not clear from the data whether the observed changes are reversible or precarcinogenic. However, these changes closely resembled the histologic features described in the evolution of bladder cancer in rats fed N-C4-(5-nitro-2-furyl)-2-thiazolyl formamide.

Animals↗