Biomedical subjects
M Armstrong
Publications and source records attributed to M Armstrong.
Shiftwork. No proper time of day.
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Busting the blood gas blues.
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High frequency epicardial echocardiography for coronary artery evaluation: in vitro and in vivo validation of arterial lumen and wall thickness measurements.
The purpose of this study was to determine the accuracy of a new high frequency echocardiographic technique for the quantitative assessment of coronary artery luminal and wall dimensions. In 32 open chest animals, high frequency echocardiographic measurements (echo) of luminal diameter correlated well with in vitro histologic measurements (Histo) (r = 0.86; high frequency echo = 0.89 Histo + 0.79) (range 1.7 to 5.8 mm). Similar results were found in the evaluation of five human autopsy hearts studied in vitro. Coronary artery wall thickness measurements in human autopsy hearts showed a good correlation with high frequency echocardiographic measurements (r = 0.86; high frequency echo = 0.65 Histo + 0.24) (range 0.3 to 0.8 mm). In eight open chest calves, high frequency echocardiographic measurements of total vessel diameter correlated well with sonomicrometer measurements (Sono) (r = 0.94; high frequency echo = 1.03 Sono + 0.4) (range 2.1 to 5.3 mm). Inter- and intraobserver variability measurements of high frequency echocardiographic measurements demonstrated excellent reproducibility (r = 0.95, interobserver variability for wall thickness; r = 0.97, interobserver variability for luminal diameter; n = 10 postmortem human coronary arteries). In conclusion, high frequency echocardiography is an accurate and reproducible method of measuring coronary luminal and wall geometry and may be a potentially useful tool for in vivo coronary artery evaluation in patients.
Occupational health hazards for dental hygienists.
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Possible relationships between changes in body weight set-point and stress metabolism after treating rats chronically with D-fenfluramine. Effects of feeding rats acutely with fructose on the metabolism of corticosterone, glucose, fatty acids, glycerol and triacylglycerol.
Rats were maintained on a corn oil diet and treated with D-fenfluramine at doses of 2.5 mg/kg twice a day for 11 days or with 10 mg or 25 mg/kg once a day for 12 days. The lower dose of D-fenfluramine produced no marked changes in body weight and after 11 days of treatment the weights of the rats on average were only 2% lower than the controls. The food intake of these rats was only decreased on the first day. The two higher doses of D-fenfluramine decreased the food consumption for about 3 days but thereafter it was similar to that of the control rats. The body weight of these rats fell on the first day, but after about four days the gain in body weight paralleled rather than approached that of the control rats. Increasing the dose of D-fenfluramine progressively decreased the relative size of the epididymal fat pad. At the end of the treatment period the rats were fed acutely with fructose to increase the circulating concentrations of corticosterone and to stimulate triacylglycerol synthesis. All three doses of D-fenfluramine decreased the concentration of circulating triacylglycerol after fructose feeding. The 10 mg/kg dose also decreased the basal concentration of triacylglycerol. The two higher doses of fenfluramine decreased the rises in the circulating concentrations of corticosterone, glycerol and fatty acids that are produced by fructose feeding. The basal concentrations of these compounds in the absence of fructose feeding were not significantly affected by the 10 mg/kg dose of D-fenfluramine. The possible relationship between the effect of chronic treatment with D-fenfluramine in decreasing a metabolic stress response and lipolysis is discussed relative to its hypotriglyceridaemic action and its effect on body weight-set point. The results demonstrate that D-fenfluramine produced persistent changes in metabolism at a time when the treated rats were growing at the same rate as the control rats and when they were eating similar quantities of food.
Laboratory diagnosis of cryptosporidiosis.
Cryptosporidium spp is now widely accepted as a cause of gastroenteritis. Various methods have been applied to detect oocysts in faeces, but the difficulties of discriminating between non-cryptosporidial bodies, acid fast bodies like cryptosporidia, and cryptosporidia remain. A simple examination in two stages, suitable for routine use is described, using auramine phenol and carbol fuchsine for screening and a modified Ziehl-Neelsen staining method for confirmation. A further method, using Jenner and Giemsa stains, is of value for confirmation of identity, especially where fluorescence microscopy is unavailable. A modification of the formol-ether method of concentration is also described. Immunofluorescence and thin section electron microscopy provide definitive identification. Vomiting can be an important clinical feature of gastroenteritis, and the first description of oocysts in vomit is reported. Preliminary findings, after more than two years of study show that Cryptosporidium is an important pathogenic agent in gastroenteritis, confirm the increased incidence in children, and suggest a possible seasonal trend.
Presentations and effective speaking.
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Soothe your practice qualms with a postdoctoral residency.
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Why the formation of an RCN ethics committee is not before time.
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Assertiveness training in fourth- and fifth-grade children.
An assertiveness training program for 343 fourth- and fifth-grade children was designed and evaluated. All children in 10 classrooms were randomly assigned by classroom to one of three conditions: (a) assertiveness training, (b) a control intervention, or (c) a no-treatment control. The intervention procedures were administered for 2 hours a week for 12 weeks in groups of 6 pupils each. Assertiveness was higher among classes receiving assertion training on the quality of alternatives generated on the Interpersonal Problem-solving Test, an Assertion Quiz and a Group Decision Task. Teachers reported better comportment and higher achievement and higher popularity among the assertion classes. Grade point averages increased for the pupils in the assertiveness group 1 year following the intervention. Observations indicated a greater number of student-initiated contacts with the teacher and fewer questions answered by the pupils receiving assertiveness training. The usefulness of assertiveness training as a primary prevention intervention is discussed.
Reactivity of cold agglutinins with subsets of human lymphocytes of various origins.
Forty-five cold agglutinins (CA) were tested against various populations of lymphocytes by cytotoxicity and immunofluorescence assays. Marked differences were observed between anti-I and anti-i CA. Thirty-six per cent of anti-I killed preferentially peripheral blood and tonsillary B lymphocytes, whereas only 12 per cent killed preferentially T lymphocytes. Anti-I killed a much higher proportion of B-chronic lymphocytic leukemia cells than peripheral blood lymphocytes, peripheral blood B cells or T-chronic lymphocytic leukemia cells. Forty-three per cent of anti-i killed preferentially peripheral blood T lymphocytes and 54 per cent killed preferentially tonsillary T cells, whereas only 14 per cent killed more peripheral blood B cells and none killed preferentially tonsillary B cells. The kill of thymic lymphocytes and T-chronic lymphocytic leukemia cells by anti-i was very high, whereas the kill of B-chronic lymphocytic leukemia cells was very low. Almost all CA of other than I-i specificities showed preferential kill of peripheral blood B (83 per cent) and tonsillary B (67 per cent) cells. Tonsillary lymphocytes were usually more susceptible to the cytotoxic activity of CA than peripheral blood lymphocytes. Cold agglutinins with kappa light chains killed more B cells whereas CA with gamma light chains seemed to kill more T cells. Cytotoxicity did not correlate to the utilization of complement. It is suggested that the density and/or the accessibility of membranous antigens may be different on B and T cells, or alternatively that in addition to antigens common to all lymphocytes, anti-I and non-I/i cold agglutinins recognize specific antigenic determinants on B lymphocytes, whereas anti-i cold agglutinins recognize specific antigenic determinants on T lymphocytes.
Avoiding orientation burn-out: a practical guide designed to help inservice instructors.
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Examination of the immunological relationship between measles virus and canine distemper virus using monospecific measles antisera.
Indirect immunofluorescence titrations were performed with measles virus, the Rockborn strain of canine distemper virus (CDV), and a large plaque variant of the Onderstepoort strain of CDV (Ond-LP) using monospecific antisera prepared against either the haemagglutinin (anti-HA), the haemolysin (anti-HL), or the ribonucleoprotein (anti-RNP) of measles virus. Tests with anti-HA showed that the Rockborn strain of CDV was more closely related to measles virus than Ond-LP. The ribonucleoprotein antigens of the CDV strains were closely related to each other but were both related to and distinct from measles virus RNP. The use of measles anti-HL serum demonstrated that CDV possesses an antigenically related acetone-sensitive component equivalent to the haemolysin of measles virus. Absorption of human convalescent serum with excess quantities of acetone-fixed CDV antigens had no effect on measles-specific anti-HA, HL, or RNP activity in the serum. Absorption with measles antigens on the other hand, totally removed all measles and CDV-specific HA and RNP activity. CDV was not neutralised by any of the monospecific antisera when tested either as individual antisera or as mixtures. Our results demonstrate the occurrence of antigenic variation between different strains of CDV, they also reveal unique antigenic determinants in both measles virus and CDV.
New antigenic determinant (Sa) on human lymphocytes and phagocytes.
Presence of antigenic determinants reacting with homogeneous IgM/kappa cold agglutinin (CA) of a new specificity, tentatively called Sa, was investigated by bithermic cytotoxicity assay and by immunofluorescence. CA Sa killed on average 38% allogeneic peripheral blood lymphocytes (PBL) and up to 74% of autologous PBL. There was preferential kill of B-PBL compared to T-PBL. Some preference toward B cells was also noted using tonsillary B and T lymphocytes. Cytotoxic activity of CA Sa against chronic lymphocytic leukemia cells of B-type was almost equal to that of potent anti-I CA and much stronger than anti-i CA. Presence of additional B-cytotoxic factor in the serum was excluded by the use of red blood cell eluate composed solely of homogeneous CA. Thymocytes and helper-type T cells from a patient with T cell chronic lymphocytic leukemia were very susceptible to the cytotoxic action of Sa. CA Sa killed 39% of monocytes, but there was almost no kill of polymorphonuclear leukocytes. Lymphocytotoxicity of CA Sa was abolished by sialyllactose and was not influenced by I-active glycoproteins. Comparison of CA Sa to CA of other specificities showed marked differences, supporting the view that Sa has new, previously unrecognized specificity.
Antigenic differences in the hemagglutinin of measles and related viruses.
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