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51.
A hemolysin that appears to be responsible for the zones of beta-hemolysis surrounding colonies of group B streptococci (Streptococcus agalactiae) on blood agar plates has been isolated and partially purified. No soluble hemolysin was detectable in the supernatants of streptococcal cultures grown in several types of media. However, hemolytic activity was detected when streptococci were incubated with erythrocytes, and soluble hemolysin was isolated when bacterial suspensions were incubated in the presence of a variety of agents, including calf serum, albumin, Tween 80, and starch. Glucose and other fermentable carbohydrates stimulated hemolysin production, and metabolic inhibitors greatly reduced the titer of hemolysin that could be recovered, suggesting that cellular metabolism is necessary for hemolysin production or release. The soluble hemolysin was concentrated by ammonium sulfate precipitation and partially purified by gel filtration. Agents known to inhibit other streptococcal hemolysins, including phospholipids, trypan blue, proteases, and cholesterol, were tested for their effect on the group B hemolysin. Only the phospholipids inhibited hemolysin activity. The group B streptococcal hemolysin appears to be similar to, but distinct from, streptolysin S produced by Streptococcus pyogenes. 相似文献
52.
A computer-interfaced photometer and systematic spacing of duplicates to control within-plate enzyme-immunoassay variation 总被引:9,自引:0,他引:9
B W Stemshorn D J Buckley G St Amour C S Lin J R Duncan 《Journal of immunological methods》1983,61(3):367-375
A Multiskan photometer for reading microtiter plate enzyme immunoassays was linked with a time sharing computer to facilitate control of assay variation and analysis of results. The interface that converted photometer output to RS-232-C format required changes to divide the output into segments short enough for input to the computer. To measure within-plate variation and investigate how the method of allocating sample duplicates to plate wells may affect the estimation of sample variance, uniformity tests were conducted with 47 plates. Coefficients of variation (CV) among wells within-plates ranged from 4.6 to 20.7% and in two-thirds of the plates exceeded 10%. Duplicates allocated to adjacent wells (method 1) gave consistently higher CV for sample means than duplicates allocated to opposite plate quadrants (method 2). In general, the CV by method 2 was about 30% smaller than that by method 1. Analysis of variance confirmed the effectiveness of the quadrant pattern of duplicate allocation as a method of controlling variation that arises from well position effects. 相似文献
53.
Cloning, expression, and mapping of the Staphylococcus aureus alpha-hemolysin determinant in Escherichia coli K-12. 总被引:7,自引:7,他引:7 下载免费PDF全文
A fragment of Staphylococcus aureus DNA encoding the alpha-hemolysin determinant was cloned from strain Wood 46 by inserting Sau3A-generated genomic DNA fragments between the BamHI sites of the lambda replacement vector L47.1. Phages expressing alpha-hemolysin were detected by overlaying plaques formed from several thousand independent recombinant phage with erythrocytes and looking for zones of hemolysis. One phage expressing alpha-hemolysin was purified and named lambda w alpha 3. This was subsequently shown to contain a 10.2-kilobase pair insert of S. aureus DNA. A 7.6-kilobase pair HindIII fragment encoding the alpha-hemolysin was subcloned from lambda w alpha 3 into the plasmid vector pACYC184 to form the hybrid plasmid pDU1148. Escherichia coli K-12 cells harboring pDU1148 synthesized a low level of alpha-hemolysin which remained associated with the cells and was not secreted into culture supernatants. When the same strain was stabbed onto blood agar plates, no zones of hemolysis were detected after overnight growth at 37 degrees C but hemolysis developed if the plates were left at room temperature for 48 h. By introducing specific deletions or Tn5 insertions into plasmid pDU1148, the alpha-hemolysin gene was mapped to a region within a 3.3-kilobase pair EcoRI-HindIII fragment which was subcloned onto the vector plasmid pBR322. A specific enzyme-linked immunosorbent assay with peroxidase-labeled rabbit anti-alpha-hemolysin antibodies was used to measure the levels of alpha-hemolysin antigen expressed in E. coli K-12 cells harboring pDU1148 or a variety of pDU1148::Tn5 and pDU1148 deletion mutants. 相似文献
54.
55.
RhoC is dispensable for embryogenesis and tumor initiation but essential for metastasis 总被引:14,自引:0,他引:14
Hakem A Sanchez-Sweatman O You-Ten A Duncan G Wakeham A Khokha R Mak TW 《Genes & development》2005,19(17):1974-1979
The Rho proteins are Ras-related guanosine triphosphatases (GTPases) that function in cytoskeletal reorganization, cell migration, and stress fiber and focal adhesion formation. Overexpression of RhoC enhances the ability of melanoma cells to exit the blood and colonize the lungs. However, in vivo confirmation of RhoC's role in metastasis has awaited a RhoC-deficient mouse model. Here we report the generation of RhoC-deficient mice and show that RhoC is dispensable for embryonic and post-natal development. We demonstrate that loss of RhoC does not affect tumor development but decreases tumor cell motility and metastatic cell survival leading to a drastic inhibition of metastasis. 相似文献
56.
Porphyromonas gingivalis, a Gram-negative oral anaerobe, interacts with epithelium lining the gingival sulcus. Continuing our studies on the role of gingipain cysteine proteinases in P. gingivalis adherence to epithelial cells, we showed that antibody raised to the recombinant adhesin domain of arg-gingipain A blocked bacterial attachment, providing new additional evidence that P. gingivalis adherence to epithelial cells is mediated by gingipain adhesin peptides. 相似文献
57.
IgA, IgM and IgG anti-M. leprae antibodies in babies of leprosy mothers during the first 2 years of life. 下载免费PDF全文
IgA, IgM and IgG anti-M. leprae antibody activity was estimated by solid phase radioimmunoassay in repeated serum samples from cord sera to sera taken 2 years after birth from 29 babies of mothers with lepromatous leprosy (Group 1) and 16 babies of mothers with tuberculoid leprosy and non-leprosy control mothers (Group 2). IgA anti-M. leprae antibody activity could be detected in 30% and IgM anti-M. leprae antibody activity in 50% of cord sera from Group 1, but not in any of the cord sera from Group 2. After birth, there was a significantly higher increase of IgA and IgM anti-M. leprae antibody activity in sera taken 3-6 months after birth from babies of Group 1 compared to Group 2, but the IgA and IgM activity in sera taken after 6 months of age showed the same increase in the two groups. IgG anti-M. leprae antibody activity showed a marked decrease in sera from both Groups 1 and 2 taken 3-6 and 6-9 months after birth compared to the activity in the cord sera. No increase of the IgG activity could be demonstrated even in sera taken 15-24 months after birth in any of the two groups. These findings are discussed in relation to possible transfer of M. leprae bacilli across the placenta, the influence of M. leprae and other mycobacteria exposure on the antibody activity, the poor IgG anti-M. leprae antibody response and subclinical leprosy infection in babies exposed to leprosy below 2 years of age. 相似文献
58.
59.
Colchicine myopathy and neuropathy 总被引:9,自引:0,他引:9
R W Kuncl G Duncan D Watson K Alderson M A Rogawski M Peper 《The New England journal of medicine》1987,316(25):1562-1568
Although colchicine has been used for centuries, its neuromuscular toxicity in humans is largely unrecognized. In this report we describe a characteristic syndrome of myopathy and neuropathy and present 12 new cases of the condition. Colchicine myopathy may occur in patients with gout who take customary doses of the drug but who have elevated plasma drug levels because of altered renal function. It usually presents with proximal weakness and always presents with elevation of serum creatine kinase; both features remit within three to four weeks after the drug is discontinued. The accompanying axonal polyneuropathy is mild and resolves slowly. Electromyography of proximal muscles shows a myopathy that is marked by abnormal spontaneous activity. Because of these features, colchicine myoneuropathy is usually misdiagnosed initially, either as probable polymyositis or as uremic neuropathy. The myopathy is vacuolar, marked by accumulation of lysosomes and autophagic vacuoles unrelated to necrosis or to the mild denervation in distal muscles. The morphologic changes in muscle suggest that the pathogenesis involves disruption of a microtubule-dependent cytoskeletal network that interacts with lysosomes. Correct diagnosis may save patients with this disorder from inappropriate therapy. 相似文献
60.
Margaret T. Duncan Ruby Husain Hui-Min Chen Steven M. Horvath 《American journal of human biology》1995,7(3):329-337
The interaction of race and climatic adaptation on patterns of cardiovascular reactivity among young adult males was examined. Malay and Chinese subjects living in a tropical climate in the Orient and Caucasians living in a sub-tropical climate in North America were investigated. The cold pressor test with hand immersion in cold water was used as the stressor. Systolic and diastolic blood pressures, cardiac frequency, cardiac output, and stroke volume were measured. The results provided limited evidence for absence of differences in cardiac reactivity among racial groups and for greater vascular reactivity in the Caucasians. Cold immersion also elicited differential responses which could be partially attributed to differences in acclimatizations status. © 1995 Wiley-Liss, Inc. 相似文献