Extensive experimental and clinical data show that the ultrasonic image conveys information on the biochemical composition of the atherosclerotic plaque, ie, the relative content of lipids (hypoechoic), fibrous tissue (hyperechoic), and calcific deposits (very echogenic with shadowing). A more dishomogeneous echo structure of the plaque is also more often associated with clinically complicated carotid plaques. To date, however, the assessment of plaque density and homogeneity by transcutaneous B-mode imaging remains subjective and qualitative. The aim of this study was to assess whether plaque echodensity and homogeneity might be established on a more objective and quantitative basis by description of the spatial distribution of echo amplitude (referred to as tissue texture) applied to digitized images, obtained with commercially available B-mode transcutaneous imaging systems. A total of 47 B-mode images derived from echotomographic studies in 10 patients were digitized off line. For each region of interest, a set of first-order (mean gray level, standard deviation, skewness, kurtosis: mathematical descriptors of the shape of the frequency distribution of gray-level histogram) and of second-order (entropy, angular moment: mathematical descriptors of the spatial distribution of gray levels within the region of interest) textural parameters were evaluated. The visual, concordant reading by two independent, experienced observers assigned the plaques on the basis of qualitatively assessed echodensity to three groups: "soft" (n = 18), "fibrotic" (n = 20), "calcific" (n = 9). Regarding spatial gray-level distribution, 46 plaques would be separated into "homogenous" (n = 17) and "dishomogeneous" (n = 29). On digitized images, the normalized mean gray level was the most effective first-order textural parameter for distinguishing soft (24.2 +/- 12.4 arbitrary units in a zero to 255 scale) from fibrotic (64.5 +/- 16.4) and calcific plaques (125.3 +/- 24.5), P < 0.01 for all intergroup differences. "Homogeneous" plaques were separated from "heterogeneous" ones on the basis of entropy (5 +/- 1 vs 7.9 +/- 9.7; P < 0.01), whereas the values of angular second moment overlapped (1.542E-3 + 1.334E-3 vs 5.181E-4 +/- 2.5615E-4, P = ns). In conclusion, quantitative texture analysis of ultrasonic images derived from transcutaneous, high-resolution, commercially available B-scan systems is feasible in man and provides a quantitative operator-independent assessment of plaque echodensity and homogeneity.
The Bursa of Fabricius of 15 day, 1-, 3-, and 6 month-old adult chickens (White Leghorn strain) were studied by histological and histochemical staining, histoenzymatic reactions (LDH, SDH, α-GPDH, NAD, NADPH, Ca ++ -dependent ATP-ase, pH 8.5) and by anti-thymostimulin immunoreaction. Positive reactions for mucopolysaccharides and enzymatic activities were located in the epithelia of the follicles, i.e. in follicleassociated-epithelium (FAE), inter-follicle-epithelium (IFE) and in different epithelial compartments of cortical and medullary zones. Positive reaction for thymostimulin-like (TSlike) substance was restricted to FAE cells and weakly to the basal lamina of IFE. In 6-month-old chickens, the FAE cells disappeared; the phenomenon of bursal regression was evident, although not all the follicles were involved. In the few still normal follicles, the good reactivity to the enzymes tested suggests that residual physiological activity is still present, even if reduced. , 1621) is a primary lymphoid organ peculiar to birds. The bursa is responsible for the maturation and differentiation of B-lymphocytes to produce humoral immunological responses. The other primary lymphoid organ, the thymus, instead, is responsible for the maturation and differentiation of T-lymphocytes, leading to cellular immunological responses (Dent and Good, 1965;Schaffner et al., 1974a;Le Douarin et al., 1984).The structure of the bursa has been described both during the ontogenetic period (Jolly, 1911a(Jolly, , 1914Cordier, 1969;Edwards et al., 1975;Le Douarin et al., 1975;Le Douarin et al., 1976;Le Douarin et al., 1984;Ritter and Lebacq, 1977) and during the posthatching period up to its involution (Jolly, 1911b(Jolly, ,1914Mc Connachie and Ruth, 1973;Glick, 1974Glick, , 1983Bellamy and Mohamed, 1982;Davenport and Allen, 1985).Since the discovery that the bursa was implicated in the differentiation of B-lymphocytes for humoral immunity (Chang et al., 1955;Glick et al., 1956;Papermaster and Good, 1962;Peterson and Good, 1965), attention was focused, on the one hand, on lymphoid cell populations (Ackermann and Knouff, 1959;Ackermann, 1962;Woods and Linna, 1965;Cooper et al., 1966; Toivanen et al., 1972 a,b;Toivanen et al., 1974;Back et al., 1973;Grossi et al., 1974;Grossi et al., 1976;Glick, 1974Glick, , 1983Glick, , 1995Glick et al., 1975;Eerola et al., 1982;Brand et al., 1983;Pink et al., 1985;Lassila, 1989;Nowak et al., 1990;Motyka and Reynolds, 1991;Petrini et al., 1991;Paramithiotis and Ratcliffe, 1993, 1994 a,b, 1996Reynaud and Weill, 1993;Masteller and Thompson, 1994;Masteller et al., 1995;Paramithiotis et al., 1995;Obranovich and Boyd, 1996;Funk and Thompson, 1996) and, on the other hand, on the epithelial stroma providing the bursal microenvironment within which B-cell maturation and differentiation occurs.
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