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91.
Contribution of CsrR-regulated virulence factors to the progress and outcome of murine skin infections by Streptococcus pyogenes 下载免费PDF全文
Streptococcus pyogenes with null mutations in the csrRS regulatory locus are highly virulent in mice due to derepression of hyaluronic acid capsule synthesis and exotoxins, e.g., streptolysin S (SLS) and pyrogenic exotoxin B (SpeB). We generated derivatives of a DeltacsrRS strain that also carry deletions in hasAB (leading to an acapsular phenotype) or in sagA (phenotypically SLS-) or an interruption of speB (SpeB-) to test the relative contributions of these factors to the development of necrotic skin lesions. Inoculation of 2 x 10(6) to 4 x 10(6) CFU of either acapsular or SLS- strains into hairless mice resulted in lesions approximately 70% smaller than those of the DeltacsrRS parent strain. Elimination of SLS also reduced lethality from 100% to 0% at this inoculum (P < 10(-7); Fisher exact test). In contrast, SLS+ SpeB- mutants yielded lesions that were only 41% smaller than the parent strain (t = 2.2; P = 0.04), but only 3 the 17 lesions had dermal sloughing (P = 10(-5)). The nonulcerative lesions associated with SpeB- strains appeared pale with surrounding erythema. We conclude that capsule and SLS contribute to the subcutaneous spread of S. pyogenes and to a fatal outcome of infection. SpeB facilitates early dermal ulceration but has minor influence on lesion size and mortality. Large ulcerative lesions are observed only when both toxins are present. 相似文献
92.
An efficient SNP system for mouse genome scanning and elucidating strain relationships 总被引:8,自引:0,他引:8 下载免费PDF全文
Petkov PM Ding Y Cassell MA Zhang W Wagner G Sargent EE Asquith S Crew V Johnson KA Robinson P Scott VE Wiles MV 《Genome research》2004,14(9):1806-1811
A set of 1638 informative SNP markers easily assayed by the Amplifluor genotyping system were tested in 102 mouse strains, including the majority of the common and wild-derived inbred strains available from The Jackson Laboratory. Selected from publicly available databases, the markers are on average ~1.5 Mb apart and, whenever possible, represent the rare allele in at least two strains. Amplifluor assays were developed for each marker and performed on two independent DNA samples from each strain. The mean number of polymorphisms between strains was 608±136 SD. Several tests indicate that the markers provide an effective system for performing genome scans and quantitative trait loci analyses in all but the most closely related strains. Additionally, the markers revealed several subtle differences between closely related mouse strains, including the groups of several 129, BALB, C3H, C57, and DBA strains, and a group of wild-derived inbred strains representing several Mus musculus subspecies. Applying a neighbor-joining method to the data, we constructed a mouse strain family tree, which in most cases confirmed existing genealogies. 相似文献
93.
Vav1: a key signal transducer downstream of the TCR 总被引:7,自引:0,他引:7
94.
95.
Bhattacharya B Sariya D Reddy VB Kluskens L Gould VE Gattuso P 《Diagnostic cytopathology》2002,26(6):384-386
A 4(1/2)-yr-old female presented with right-sided pleural effusion and a retroperitoneal mass. Cytologic analysis of the pleural fluid yielded malignant small round blue cells, which were noncohesive, 3-4 times the size of lymphocytes. The malignant cells had hyperchromatic, pleomorphic nuclei with moderate amounts of vacuolated cytoplasm. A few fiber-shaped cells were also seen. Immunostains for desmin, muscle-specific actin were positive; ultrastructural findings of thick and thin actin-myosin filaments confirmed the diagnosis of embryonal rhabdomyosarcoma. This case illustrates the importance of performing appropriate immunohistochemical stains and ultrastructural studies on cytological material to arrive at a definitive diagnosis. 相似文献
96.
L. Maximilian Buja Victor J. Ferrans Barry J. Maron 《The American journal of pathology》1974,74(3):613-648
Junctional structures formed by two parts of the plasma membrane of the same cardiac muscle cell were observed in ventricular myocardium of: a) patients with neoplasms, aortic valvular disease or idiopathic hypertrophic subaortic stenosis and b) dogs subjected to prolonged normothermic anoxic cardiac arrest. Most of these structures had features of desmosomes; other, more complex structures had components with features of desmosomes, fasciae adherentes and nexuses, and, therefore, resembled intercalated discs. These intracytoplasmic junctions were localized to: a) the peripheral cytoplasm at the sides or ends of cells, b) narrow invaginations of plasma membranes, c) narrow zones of deep, broad plasmalemmal invaginations and d) narrow branches of T tubules. In patients with idiopathic hypertrophic subaortic stenosis or aortic valvular disease and in the dogs subjected to anoxic cardiac arrest, intracytoplasmic junctions were observed in hypertrophied or degenerated muscle cells which were located in areas of fibrosis and which showed loss of contact with adjacent cells. In patients with neoplasms, intracyto-plasmic junctions were found in degenerated cells which were located in areas of interstitial edema and which also showed loss of contact with adjacent cells. Our observations suggest that remodeling of cell surfaces following loss of intercellular contact is the most likely mechanism of formation of intracytoplasmic junctions. 相似文献
97.
Sympathetic overactivity in patients with chronic renal failure. 总被引:23,自引:0,他引:23
R L Converse T N Jacobsen R D Toto C M Jost F Cosentino F Fouad-Tarazi R G Victor 《The New England journal of medicine》1992,327(27):1912-1918
BACKGROUND: Hypertension is a frequent complication of chronic renal failure, but its causes are not fully understood. There is indirect evidence that increased activity of the sympathetic nervous system might contribute to hypertension in patients with end-stage renal disease, but sympathetic-nerve discharge has not been measured directly in patients or animals with chronic renal failure. METHODS: We recorded the rate of postganglionic sympathetic-nerve discharge to the blood vessels in skeletal muscle by means of microelectrodes inserted into the peroneal nerve in 18 patients with native kidneys who were undergoing long-term treatment with hemodialysis (of whom 14 had hypertension), 5 patients receiving hemodialysis who had undergone bilateral nephrectomy (of whom 1 had hypertension), and 11 normal subjects. RESULTS. The mean (+/- SE) rate of sympathetic-nerve discharge was 2.5 times higher in the patients receiving hemodialysis who had not undergone nephrectomy than in the normal subjects (58 +/- 3 vs. 23 +/- 3 bursts per minute, P < 0.01). In contrast, the rate of sympathetic-nerve discharge was similar in the patients receiving hemodialysis who had undergone bilateral nephrectomy (21 +/- 6 bursts per minute) and the normal subjects. The rate of sympathetic-nerve discharge in the patients receiving hemodialysis who had not undergone nephrectomy was also significantly higher (P < 0.01) than that in the patients with bilateral nephrectomy, and it was accompanied in the former group by higher values for vascular resistance in the calf (45 +/- 4 vs. 22 +/- 4 units, P < 0.05) and mean arterial pressure (106 +/- 4 vs. 76 +/- 14 mm Hg, P < 0.05). The rate of sympathetic-nerve discharge was not correlated with either plasma norepinephrine concentrations or plasma renin activity. CONCLUSIONS: Chronic renal failure may be accompanied by reversible sympathetic activation, which appears to be mediated by an afferent signal arising in the failing kidneys. 相似文献
98.
Joseph Niezette Nikos Hadjichristidis Victor Desreux 《Macromolecular chemistry and physics.》1976,177(7):2069-2078
Trityl methacrylate was polymerized with 2,2′-azodiisobutyronitrile at 60°C in a homogeneous hexamethylphosphoric triamide (HMPT) solution. The isotactic microstrucutre found by NMR spectroscopy was less important for this polymer than for poly(trityl methacrylate) prepared in benzene, a precipitating medium. Some aspects of the hydrodynamic behaviour of poly(trityl methacrylate) were examined in HMPT at 25°C. Relations between the intrinsic viscosity, the root-mean-square end-to-end dimension, and the weight average molecular weight were established. The unperturbed dimension 〈r 〉1/2 was determined from viscosity and light scattering measurements using the well known extrapolation methods of Kurata-Stockmayer, Stockmayer-Fixman, Cowie, Inagaki-Kurata, and Baumann. Poly(trityl methacrylate) adopts a moderately expanded conformation in HMPT at 25°C. The correlation of the chain rigidity with the molar volume of the side group of polymethacrylic esters shows that poly(trityl methacrylate) has a higher chain rigidity than other polymethacrylates on account of the steric hindrance of the trityl group and of the strong interactions between the aromatic rings. 相似文献
99.
We examine the responses of single neurons and pairs of neurons, simultaneously recorded with a single tetrode in the primary visual cortex of the anesthetized macaque monkey, to transient presentations of stationary gratings of varying spatial phase. Such simultaneously recorded neurons tended to have similar tuning to the phase of the grating. To determine the response features that reliably discriminate these stimuli, we use the metric-space approach extended to pairs of neurons. We find that paying attention to the times of individual spikes, at a resolution of approximately 30 ms, and keeping track of which neuron fires which spike rather than just the summed local activity contribute substantially to phase coding. The contribution is both quantitative (increasing the fidelity of phase coding) and qualitative (enabling a 2-dimensional "response space" that corresponds to the spatial phase cycle). We use a novel approach, the extraction of "temporal profiles" from the metric space analysis, to interpret and compare temporal coding across neurons. Temporal profiles were remarkably consistent across a large subset of neurons. This consistency indicates that simple mechanisms (e.g., comparing the size of the transient and sustained components of the response) allow the temporal contribution to phase coding to be decoded. 相似文献
100.
Transcytosis and catabolism of antibody 总被引:10,自引:0,他引:10
This review describes the evolution of our knowledge of the transmission of immunoglobulin G (IgG) from mother to infant and
the factors which regulate the persistence of IgG in the circulation. These apparently unrelated processes involve the same
Fc receptor, FcRn (n=neonatal). FcRn appears to carry out these diverse roles by binding to IgG and then either transporting
the bound IgG across cells (transcytosis) or recycling its cargo back to the cell surface (control of catabolism). IgG that
is taken up by cells in the absence of binding to FcRn undergoes degradation. Thus, FcRn is the “protective” receptor that
servesto maintain IgG homeostasis and deliver IgGs across cellular barriers. 相似文献