Discrimination of Strains of Salmonella enteritidis with Differing Levels of Virulence by an In Vitro Glass Adherence Test

The objective of this study was the in vitro differentiation of isolates of Salmonella enteritidis whose virulences differed in a chick model. A total of 14 strains of S. enteritidis were isolated from either the environment, dairy products, or infected patients. The isolates could be divided into two groups on the basis of their virulence (50% lethal dose) in chickens infected intraperitoneally. When the strains were incubated in adherence test medium (Spanish patent 9700408), only the virulent strains produced aggregates and formed visible filaments attached to the glass tube. These results suggest, although for a limited number of strains, that aggregation in such a medium could be used as a diagnostic tool to discriminate virulent strains of S. enteritidis.     

Mechanical Contribution of Endocardium During Finite Extension and Torsion Experiments on Papillary Muscles

Finite extension and torsion tests on cardiac papillary muscles are presently the best way to directly measure the response to shear along myocardial fibers. Quantifying this response is necessary for determining the complete three-dimensional constitutive behavior of myocardium as a transversely isotropic material. Analysis of such tests is complicated, however, since papillary muscles are materially inhomogeneous, consisting of a myocardial core surrounded by an endocardial sheath that is rich in collagen. In this article, we show that the papillary muscle response to extension and torsion additively decouples into the response of the bare myocardial core plus the response of an endocardial sheath filled with fluid (assuming the muscle is a radially inhomogeneous and incompressible continuum with cylindrical symmetry). This result allows the endocardial response to be subtracted from the intact papillary muscle response to obtain the response of the bare myocardial core. An initial estimate suggests that the endocardial sheath affects the axial moment significantly (50% of torque for all twists at low stretch) but affects the axial force only slightly (<10% at moderate twists). © 1999 Biomedical Engineering Society. PAC99: 8719Hh, 8719Rr, 8719Ff     

Respiratory syncytial virus associated illness in high-risk children and national characterisation of the circulating virus genotype in South Africa.

BACKGROUND: There is limited information about respiratory syncytial virus (RSV) in high-risk children from developing countries or on the genotype characterisation of the circulating virus. OBJECTIVE: To define the proportion of children with RSV associated lower respiratory tract infections (LRTI) that had risk factors for severe disease and to genotype the circulating RSV strains across the country. STUDY DESIGN: A prospective study was performed in four distinct regions. During April 2000-December 2000 (period 1), all children, with LRTI or without underlying high risk factors for severe RSV disease were enrolled. During January to September 2001 (period 2), only children with LRTI with underlying high risk factors were enrolled. Nasopharyngeal aspirates were evaluated for RSV infection using an ELISA test. RSV isolates were also subtyped and genotyped. RESULTS: Fifty three (24%) of 220 children enrolled during period 1 had risk factors for severe RSV disease; in addition to which a further 38 high-risk children were enrolled during 2001. RSV was isolated from 16 (30%) of 53 and 37 (22%) of 167 high-risk and non-high risk children, respectively, P=0.31. High-risk children were more likely to require intensive unit care (25 vs. 2.7%, P=0.02) and were also more likely to be hospitalised for a longer duration (median 7 vs. 5 days, P=0.06) than non high-risk infants. Overall (periods 1 and 2), RSV was isolated from 34 (37.4%) of the 91 high-risk infants enrolled. Among high-risk children, those from whom RSV was isolated were more likely to require hospitalisation (73.5 vs. 54.4%, P=0.07) and admission to an intensive care unit (14.7 vs. 1.8%, P=0.03) than those from whom RSV was not isolated. Of 40 isolates subtyped during period one, 92.5% were subtype A. Further, 27 (83.3%) of 30 subtype A isolates genotyped during period 1 clustered with GA2. CONCLUSION: RSV is an important cause of LRTI among high-risk infants in a developing country such as South Africa. For the season in question, the genotype that was dominant in Johannesburg was isolated throughout the country, suggesting that successful genotypes may have the ability to spread nationwide.     

Pulmonary carcinomas with a sarcomatoid element: an immunocytochemical and ultrastructural analysis

Eight primary carcinomas of the lung with a prominent spindle-cell sarcomatoid component were studied by immunocytochemical staining and electron microscopy. The eight tumors were indistinguishable by conventional light microscopy, with the exception of one unusual neoplasm that followed multiple pathways of differentiation with elements of squamous cell carcinoma, rhabdomyosarcoma, chondrosarcoma, and an undifferentiated spindle-cell population. Reticulin fiber production by individual spindle cells and a sharp demarcation of the carcinomatous and sarcomatoid domains by light microscopy were not useful differentiating features. Three of the eight tumors exhibited keratin expression in both the carcinomatous and spindle-cell components. Both immunocytochemical and electron microscopic analyses were required to detect epithelial differentiation, as in one case keratin was identified only by immunocytochemical staining and in another only by ultrastructural examination. Epithelial differentiation was undetectable in the sarcomatoid component of five tumors, and in one case immunoreactive myoglobin was identified in spindle cells; skeletal muscle differentiation was confirmed ultrastructurally. We propose that pulmonary carcinomas exhibiting evidence of epithelial differentiation in a sarcomatoid component be termed spindle-cell carcinomas and that those biphasic tumors exhibiting mesenchymal differentiation into specific tissues, such as neoplastic bone, cartilage, or striated muscle, or lacking epithelial differentiation by light microscopy, immunocytochemistry, and electron microscopy be classified as carcinosarcomas. This distinction may ultimately be unnecessary, because these two tumors may represent different points along a morphologic and biologic continuum.     

Disconnected optic axons persist in the visual pathway during regeneration of the retino-tectal projection in the frog

Summary In this study, we crushed one optic nerve in the frog Litoria (Hyla) moorei and at intervals thereafter anterogradely labelled optic axons with horseradish peroxidase (HRP). For one series, HRP was applied between the eye and the crush site and in a second series between the crush site and the chiasm. A tectal projection of regenerating axons was seen in both series but, in addition, up to 12 weeks post-crush, the second series displayed an additional projection. Its appearance matched that of the disconnected, but persisting, optic axon terminals which are found after enucleation or optic nerve ligation. We conclude that, in the frog, many disconnected optic axons persist throughout the period of optic nerve regeneration and of restoration of an orderly retino-tectal map.Abbreviation HRP horseradish peroxidase     

The development of harmonic distortion in pulsed finite-amplitude ultrasound passing through liver

The progressive development of finite-amplitude distortion of ultrasonic pulses has been investigated in excised bovine liver using pulsed focused ultrasonic beams at nominal frequencies of 2.5 and 3.5 MHz. Both the transducers and the powers used were those which may be encountered with clinical imaging equipment. Significant distortion of the waveform was observed to occur, particularly at higher powers. For example, at 2.5 MHz, with a mean input pressure (p0) of 0.58 MPa, the second harmonic in the pulse spectrum showed a maximum value of 10.5 dB below the fundamental and the highest third harmonic component was 19 dB below the fundamental. These particular observations illustrate that finite-amplitude distortion may be of considerable significance in the transmission through tissue of ultrasonic pulses during diagnostic scanning.     

Different macrophage populations distinguished by means of fluorescent polysaccharides. Recognition and properties of marginal-zone macrophages

Fluorescent conjugates of hydroxyethyl (OEt) starch or Ficoll are selectively ingested and retained in vivo by spleen marginal-zone (MZ) and lymph node marginal-sinus macrophages of mice, whereas similar conjugates of type 3 pneumococcal capsular polysaccharide (SIII) are generally retained by macrophages (Kupffer cells, histiocytes, macrophages of spleen, lymph nodes, bone marrow and peritoneal cavity). MZ and other macrophages are readily identifiable by fluorescence after injection in vivo of OEt starch and SIII labeled with tetraethylrhodamine isothiocyanate and fluorescein isothiocyanate. Collagenase digestion was required for recovery of intact MZ macrophages from spleen in single cell suspensions and for maximum yields of other macrophages. MZ macrophages are larger and morphologically distinct from other macrophages, but resemble them in respect of EA, EAC receptors and acid phosphates and nonspecific esterase content and are equally radio-resistant. They appear normal in CBA/N nude and in beige mice. Freshly isolated MZ macrophages in suspension have adherent lymphocytes, dispersible by EDTA treatment, with B but not T cell markers. It is suggested that selective adherence to MZ macrophages is a factor in determining B cell traffic. MZ macrophages did not have demonstrable surface I-A or I-EC antigens. Only 4–8% of other spleen macrophages freshly isolated by collagenase treatment expressed I-A in the same preparation, whereas 35% of other cells (lymphocytes and blasts) reacted with monoclonal anti-I-A and anti-I-EC. After adherence to glass or plastic, 40% or more red-pulp, but not MZ macrophages, became I-A-positive. When taken from mice recently restimulated with sheep erythrocytes, half the red-pulp macrophages expressed I-A even before adherence. The relation of MZ to other macrophages is not known. However, their properties are consistent with the demonstrated ability of thymus-independent antigens selectively taken up by these cells to elicit long-lasting IgM antibody responses by direct interaction with B cells. The unexpected observation that only a small proportion of spleen macrophages freshly isolated from unstimulated mice had detectable surface I-A, but that this proportion was much increased after attachment to plastic, is discussed in relation to the possibility that macrophages do not express surface Ia antigens unless they have been stimulated.