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51.
52.
J.W. Coleman 《Immunology letters》1982,5(4):197-201
Two types of inhibition of basic peptide-induced rat mast cell secretion are reported. Pretreatment of rat peritoneal mast cells with Vibrio comma neuraminidase, an enzyme which cleaves sialic acid from oligosaccharides, led to inhibition of 5-hydroxytryptamine release induced by the basic peptides polylysine, corticotropin1–24 and a decapeptide sequence of human IgE. Inhibition was similarly observed when mast cells were challenged in the presence of the cationic cell membrane-active substance benzalkonium chloride. It is postulated that both of these experimental procedures inhibit basic peptide-induced secretion by depletion of cell surface negative charge. Sialic acid itself does not act as a specific receptor for basic peptides, since a molar excess of sialic acid in free solution failed to inhibit secretion by binding to basic peptides in the fluid phase. 相似文献
53.
Thirty strains of streptococci were tested for lysis with lysozyme, and 29 of these could be lysed by the following method: (i) suspension of the cells to a Klett reading of 200 units (no. 42 filter) in 0.01 m tris(hydroxymethyl)aminomethane buffer, pH 8.2, after washing twice with the buffer; (ii) addition of lysozyme to a final concentration of 250 mug/ml with incubation for 60 min at 37 C; (iii) addition of sodium lauryl sulfate (SLS) to a final concentration of 0.2% and incubation up to an additional 15 min at 37 C. Significant lysis was obtained only after the addition of SLS. (Strains of groups A, E, and G were treated with trypsin at a concentration of 200 mug/ml for 2 hr at 37 C before exposure to lysozyme.) These parameters for optimal lysis of streptococci by lysozyme were established by testing the group D Streptococcus faecalis strain 31 which lyses readily with lysozyme and the group H strain Challis which is less susceptible to the action of the enzyme. Viability of S. faecalis decreased 96% after 3 min of exposure to 250 mug of lysozyme per ml, whereas the more resistant strain Challis retained 27% of the initial viability after the same period. After 60 min, there was almost total loss of viability in each case. Variations of three methods of lysing streptococci with lysozyme were compared with respect to the decrease in turbidity and the release of protein and deoxyribonucleic acid (DNA) effected by each variation. The method presented in this paper allowed the greatest release of these cytoplasmic constituents from S. faecalis and strain Challis. Transformation experiments using DNA obtained from strain Challis (streptomycinresistant) by this method showed that the DNA released is biologically active. 相似文献
54.
Use of antisera to epithelial membrane antigen for the cytodiagnosis of malignancy in serous effusions. 总被引:4,自引:5,他引:4 下载免费PDF全文
A To D V Coleman D P Dearnaley M G Ormerod K Steele A M Neville 《Journal of clinical pathology》1981,34(12):1326-1332
A new human antigen, designated epithelial membrane antigen (EMA), has recently been described on surface membranes of a wide variety of normal epithelium but not on connective tissue cells. The antigen is only weakly expressed on normal or reactive mesothelium. Increased expression of the antigen has been observed in most neoplasms of epithelial origin and in malignant mesothelioma. We have investigated the possibility of using this difference in the expression of the antigen to distinguish between mesothelial cells and malignant cells in cytological smears of serous effusions. This distinction cannot always be made on morphological grounds alone and problems of differential diagnosis are encountered in about 15% of all specimens of serous effusions sent for cytological examination. Using antisera to EMA we have applied an indirect immunoalkaline phosphatase technique to alcohol-fixed smears prepared from serous effusions and have found that intense staining of the antigen is confined to effusions from patients in whom there is either clinical or cytological evidence of malignancy. The technique proved to be especially useful in cytologically equivocal cases, where there were problems of differential diagnosis. 相似文献
55.
The data in the two companion papers (McDowell et al., 1985a,b) are of a commonly occurring type in which the dependent variable takes on one of a small number of distinct values; we wish to compare the relative proportions in which these values occur. Student's test is inapplicable. We explain here in detail the linear logistic model that is appropriate, using our data as an example. Several reasonable models must first be fit. We did this by the maximum likelihood method, using a computer. We then used a chi 2 test to decide statistically between models. This process amounts to deciding directly which of the independent variables are important in determining the outcome, and thus it is the center of physiologic interest. The outcome depends on the initial choice of parametrization of the model. Generalizations are required in more complicated, but still commonly occurring, types of data. 相似文献
56.
57.
A de novo interstitial deletion of chromosome 10, del(10)(pter----q25.2::q26.1----qter), was detected in a newborn female with facial anomalies, failure to thrive, and subsequent developmental delay. This case is compared with 10 previous reports of monosomy 10q within the q25----qter region. 相似文献
58.
Deatly AM Coleman JW McMullen G McAuliffe JM Jayarama V Cupo A Crowley JC McWilliams T Taffs RE 《Virology》1999,255(2):221-227
Mice transgenic with the human poliovirus receptor gene develop clinical signs and neuropathology similar to those of human poliomyelitis when neurovirulent polioviruses are inoculated into the central nervous system (CNS). Factors contributing to disease severity and the frequencies of paralysis and mortality include the poliovirus strain, dose, and gender of the mouse inoculated. The more neurovirulent the virus, as defined by monkey challenge results, the higher the rate of paralysis, mortality, and severity of disease. Also, the time to disease onset is shorter for more neurovirulent viruses. Male mice are more susceptible to polioviruses than females. TGM-PRG-3 mice have a 10-fold higher transgene copy number and produce 3-fold more receptor RNA and protein levels in the CNS than TGM-PRG-1 mice. CNS inoculations with type III polioviruses differing in relative neurovirulence show that these mouse lines are similar in disease frequency and severity, demonstrating that differences in receptor gene dosage and concomitant receptor abundance do not affect susceptibility to infection. However, there is a difference in the rate of accumulation of clinical signs. The time to onset of disease is shorter for TGM-PRG-3 than TGM-PRG-1 mice. Thus, receptor dosage affects the rate of appearance of poliomyelitis in these mice. 相似文献
59.
60.
Measurement of passive membrane parameters with whole-cell recording from neurons in the intact amphibian retina 总被引:4,自引:0,他引:4
1. Whole-cell recordings have been obtained from intact, photoactive retinal neurons using patch-clamp electrodes in the amphibian superfused retina eyecup preparation. 2. After removal of the vitreous humor from the surface of the retina, using a collagenase with low tryptic activity, high-resistance seals (1-10 G omega) could be formed between the patch pipette and the cell membrane by applying mild suction to the pipette. Additional suction broke the membrane patch and provided continuity between the low-resistance pipette and the interior of the neuron. 3. Measurements of input resistance and time constant were obtained from bipolar, amacrine, and ganglion cells. Assuming the membrane capacitance was 1 microF/cm2, time constant data were used to derive the specific membrane resistance. The average specific membrane resistance for the inner retinal neurons in our sample was 68,000 omega.cm2. 4. Analysis of the charging curve induced by a brief current pulse applied to the soma was used to analyze the average electrotonic length of dendrites. The charging curves of some ganglion cells were well represented by a single exponential, suggesting that they were essentially isopotential. 5. The voltage decay along an equivalent cylinder model of a ganglion cell was calculated, using the experimentally obtained values of membrane resistance to compute decay of steady-state voltages along the dendritic tree. The calculations indicate that with the high membrane resistance values implied by this study, the electrotonic length of dendritic cables were short, and there may be relatively little attenuation of the synaptic potentials irrespective of their location along the dendritic tree. 相似文献