Vortex nozzle interaction in solid rocket motors: A scaling law for upstream acoustic response.

In solid rocket motors, vortex nozzle interactions can be a source of large-amplitude pressure pulsations. Using a two-dimensional frictionless flow model, a scaling law is deduced, which describes the magnitude of a pressure pulsation as being proportional to the product of the dynamic pressure of the upstream main flow and of vortex circulation. The scaling law was found to be valid for both an integrated nozzle with surrounding cavity and a nozzle geometry without surrounding cavity that forms a right angle with the combustion chamber side wall. Deviations from the scaling law only occur when unrealistically strong circulations are considered.

Urokinase plasminogen activator, a strong independent prognostic factor in breast cancer, analysed in steroid receptor cytosols with a luminometric immunoassay.

Urokinase plasminogen activator (uPA) is involved in the activation of different proteases which participate in the degradation of extracellular matrix, thereby enhancing the invasive capacity of tumour cells. uPA has been shown to be of prognostic importance in breast cancer. We have analysed uPA with a new luminometric immunoassay (LIA), applicable in cytosol samples routinely used for oestrogen-receptor (ER) and progesterone-receptor (PgR) analyses. At a cut-off value of 0.62 ng uPA/mg protein, 33% (230/688) samples were classified as representing high uPA tumours. High uPA content was found to be associated with shorter recurrence-free survival (median observation time: 42 months), ER and PgR negativity, increased p53 expression, DNA non-diploidy and a high S-phase fraction (SPF), but not with lymph node involvement or tumour size (< or = 20 mm versus > 20 mm). In the subgroup of patients not treated with systemic adjuvant therapy, multivariate analysis showed uPA to be an independent prognostic factor together with lymph node status and SPF. If these results can be reproduced, uPA may be a factor suitable for inclusion in a prognostic index.

Human antibody response to the major adhesin of Mycoplasma pneumoniae: increase in titers against synthetic peptides in patients with pneumonia.

Peptides corresponding to parts of the P1 protein (major adhesin) of Mycoplasma pneumoniae were synthesized. On the basis of predicted antigenicity, seven sequences containing 17 to 21 amino acids were selected. In addition, one peptide containing a sequence of 13 amino acids shown to be related to cytadherence of M. pneumoniae was included. Serum samples from 56 patients with pneumonia were tested for a rise in titers of specific IgG during infection, using the peptides as coating antigens in ELISA. A titer rise against one or more peptides was observed in 10 out of 13 patients with serological evidence of mycoplasmal etiology. Specific antibodies to two or more peptides were demonstrated in three patients, whereas seven patients responded to one peptide only. In the sera from patients with pneumonia of non-mycoplasmal etiology, no titer rises above the cut-off level were observed. Our results indicate that a combination of four peptides would be possible for use as antigen for serological diagnosis of infections with M. pneumoniae.

ELISA for detection of Mycoplasma pneumoniae antigens using monoclonal antibodies.

Seven monoclonal antibodies directed against major antigens of Mycoplasma pneumoniae were selected for the development of an antigen detection assay. Three of these were directed to the 170,000-dalton adhesin of M. pneumoniae. The test was an antigen-capture enzyme immunoassay using the different monoclonal antibodies for capture of antigen and a polyclonal rabbit antiserum as detection reagent. With three of the monoclonal antibodies a detection limit of approximately 2 ng M. pneumoniae protein was obtained, as determined by titration of M. pneumoniae organisms in buffer. The detection limit of the assays was only slightly less when the other four monoclonal antibodies were used. In artificially infected nasopharyngeal aspirates the detection limit was approximately 10 times lower. The fact that no significant differences in the detection limit of the assays were recorded using monoclonal antibodies directed against different antigens indicates that these antigens were available for reaction with antibodies irrespective of their location in intact M. pneumoniae cells. In the assay there were no significant cross-reactions with a number of bacterial species potentially colonizing the respiratory tract, except for a protein A-positive strain of Staphylococcus aureus. Our test is equally sensitive to another recently described ELISA using polyclonal antibodies. In comparison with other recommended methods such as immunoblot and culture-amplified antigen detection assays, the ELISA is more rapid and less laborious.

Elimination of mycoplasmas from mouse myeloma cells by intraperitoneal passage in mice and by antibiotic treatment.

Intraperitoneal passage in mice and antibiotic treatment were evaluated alone and in combination for elimination of mycoplasma contamination of mouse myeloma cell cultures. Intentional infections were established by inoculating Mycoplasma arginini, M. fermentans, M. hyorhinis and M. orale into cell cultures. Successful elimination of mycoplasmas was achieved with all strains tested by intraperitoneal passage in mice, however, cells infected with M. hyorhinis did not survive the infection long enough to be tested. Clindamycin and lincomycin cured cells infected with M. arginini, M. hyorhinis, M. orale but not M. fermentans. M. fermentans were resistant to all antibiotics tested, but could be partially suppressed by clindamycin long enough to permit curing by in vivo passage. M. arginini was eliminated by all antibiotics tested. In vivo passage and treatment with antibiotics is an efficient combination of methods for mycoplasma elimination from cell cultures and has the advantage of being simple and inexpensive.

Demonstration of membrane association and surface location of Mycoplasma pneumoniae antigens using monoclonal antibodies.

We examined 10 monoclonal antibodies (mAbs) directed against Mycoplasma pneumoniae proteins of 200, 170, 67, 46 and 42 kDa, and one mAb directed against a glycolipid component. The membrane association of the antigens reacting with our mAbs was investigated, in particular by phase-fractionation involving use of the detergent Triton X-114. The 170 kDa protein was shown to be membrane-associated, and surface exposure of this antigen was demonstrated by its disappearance from SDS-PAGE patterns after treatment of intact mycoplasmas with proteolytic enzymes. Cross-reactions with protein antigens of Mycoplasma genitalium were also shown. A mAb directed against a component of a lipid extract, prepared by the method used for preparation of the antigen used in the complement fixation (CF) test for serological diagnosis of M. pneumoniae infection, reacted with one major and a few minor bands in thin-layer chromatography (TLC) of the crude extract. The glycolipid character of this major antigen was demonstrated by treatment of the extract with sodium periodate, and by development of the TLC with orcinol/ferric chloride. These reactive bands were the same as those detected by the use of polyclonal mouse antiserum and a human convalescent serum, a result showing that the CF antigen contains a glycolipid moiety reacting with our mAb. The surface exposure of this antigen was demonstrated by binding of mAbs to intact cells.

IgG response to Mycoplasma pneumoniae in patients with community-acquired pneumonia determined by ELISA.

In a prospective study of community-acquired, radiologically verified pneumonia, a solubilized mycoplasma antigen was used in an enzyme-linked immunosorbent assay (ELISA) for the detection of IgG-antibodies to Mycoplasma pneumoniae in paired sera from 60 patients. All of the 13 patients with a positive complement fixation (CF) test for M. pneumoniae were positive in the ELISA, and 46 out of 47 patients with a negative CF test were negative. The only false positive test was recorded from a patient with a positive CF test for Chlamydia. Specific IgG antibodies were also determined in paired sera from 50 pneumonia patients, all positive in the CF test for M. pneumoniae, and collected over a period of 10 years. Of these 50 patients, 45 were recorded as positive in the ELISA for IgG antibodies to M. pneumoniae. In the prospective as well as in the retrospective study, the time for admission to hospital after onset of disease showed considerable variation (1-14 days), with the consequence that high titers were recorded in the CF as well as in the ELISA in some of the first serum samples. A tendency to earlier detection of significant titers was noted in the CF test as compared to the ELISA.

Enzyme-linked immunosorbent assay for detection of Mycoplasma pneumoniae specific immunoglobulin M.

An ELISA was developed for the detection of IgM antibodies to Mycoplasma pneumoniae in human sera, using microtiter plates coated with rabbit antiserum to human IgM selecting for IgM antibodies in the first reaction step. The specific antibodies were detected using enzyme-labelled, detergent-solubilized antigen. The complement fixation test was used as reference method. In a prospective study of 59 patients with community-acquired pneumonia, 13 of whom had evidence of mycoplasmal etiology, the ELISA was shown to have high specificity (97%). In samples taken seven days after onset of the disease all complement-fixation positive samples (n = 20) but one were positive, demonstrating the diagnostic value of a positive test in samples taken after that period.

Detection of specific IgM antibodies for the diagnosis of Mycoplasma pneumoniae infections: a clinical evaluation.

The diagnostic value of detection of specific IgM antibodies was analysed in Mycoplasma pneumoniae infections. In a retrospective clinical and serological study, M. pneumoniae IgM antibodies were determined by a mu-capture ELISA using enzyme-labelled antigen. The study group consisted of 91 patients with significantly raised titers in paired sera or a single high titer of complement fixation antibodies. About 40% of the patients had been treated with antibiotics ineffective against M. pneumoniae infections prior to admission to hospital. Treatment with erythromycin or tetracycline was shown to give a shorter period of fever compared to if no or ineffective therapy was given. Specific IgM antibodies were detected in about 80% of sera sampled 9 days or more after onset of symptoms. In sera sampled at 7-8 days after onset IgM antibodies were found in about 40% of the sera but only occasionally in sera sampled earlier. In the age group 0-20 years 88% of the patients developed an IgM response. In the higher ages (greater than 60 years) a significantly lower rate of IgM responders was observed.