Indirect Capture Research Articles

Separation of natural populations of coliform bacteria from freshwater and sewage by magnetic-bead cell sorting

Physical separation of natural populations of bacteria from a variety of environments via lectin-mediated magnetic bead separation was undertaken with the aim of obtaining a very clean population of target indigenous bacterial cells suitable for subsequent culture or molecular biological procedures. Recoveries varied with sample type, and were only effective from samples that contained a high culturable population on a general heterotroph agar (R2A) and on MacConkey agar. It was found that use of the lectin concanavalin A enabled selective recovery of coliform bacteria. Escherichia coli was separated with total coliforms, but was not preferentially selected. Separation using indirect magnetic capture was more effective and reliable than direct capture achieved using pre-labelled magnetic beads. The method may ultimately be of use in a monitoring procedure or targeted sampling programme.

Prospective evaluation of 618 pregnant women exposed to parvovirus B19: Risks and symptoms

Objective: To assess the risk of maternal parvovirus B19 infection from exposure to various sources and the fetal morbidity of those infections. Methods: We obtained demographic and occupational information about pregnant women exposed to sources of B19 and about the nature and duration of the exposures. We performed serologic testing 10–14 days after exposure using an indirect capture enzyme-linked immunosorbent assay. Women with immunoglobulin (Ig) M were examined with weekly ultrasound until 12 weeks after exposure, and the outcome of the pregnancy was ascertained from interviews with patients and their obstetricians. Logistic regression analysis was used to determine risk factors for maternal immunity and infection by B19. Results: Of 618 pregnant women exposed, 307 (49.7%) were immune to B19, 259 remained susceptible after exposure, and 52 (16.7% of all susceptibles) contracted B19 infection. None of the 52 fetuses of infected women developed nonimmune hydrops, and there were no fetal deaths attributable to B19 in this group. The relative risk of maternal B19 infection was 2.8 if the source was a related child living in the household (95% confidence interval 1.7,4.6; P < .001). No significant differences were found for maternal B19 infection in eight categories of maternal occupation. Maternal symptoms of polyarthralgia (46%), fever (19%), and nonspecific rash (38%) were significantly more common ( P < .001) in IgM-positive patients than in noninfected women (4.1%, 2.8%, and 5.7%, respectively). Only 17 (33%) of the IgM-positive women were entirely asymptomatic. Conclusion: The risk of maternal B19 infection in pregnancy could not be predicted by a gravida's occupation, but it was significantly higher when the source of exposure was her own child. The fetal risk of nonimmune hydrops after maternal B19 infection must be very low. As a consequence, exclusion of pregnant women from the workplace during endemic periods with seasonal clusters of cases is not justified. Weekly fetal ultrasound evaluation in these cases carries a low yield.

Electron-Phonon Scattering in Si-Doped GaN

ABSTRACTPhonon-plasmon scattering in non-resonant Raman spectroscopy is used to determine the free electron concentration in Si doped GaN films. For various doping concentration and variable temperature the correlation with magneto-transport data is established. The freeze-out of the carrier concentration at low temperature is thus observed in a purely optical detection scheme. We observe a very long transient time of several hours for the carrier concentration as a reaction to temperature variation. This indicates an indirect capture and emission process with a very small cross section. The value of the Faust-Henry coefficient is determined.

Assay for Recombinant and Native Human Intraacrosomal Antigen SP‐10

To develop a method to measure a recombinant sperm protein, SP-10, during scale up and purification for a contraceptive vaccine formulation. A quantitative assay method for the human intraacrosomal protein SP-10 was developed utilizing the format of indirect capture enzyme-linked immunosorbent assay (ELISA). A SP-10 specific monoclonal antibody mAb, MHS-10, was used as the capture antibody. Two recognition reagents, a rabbit polyclonal anti-SP-10 antisera (pAb) and a biotin-labeled mAb, MHS-10, were used as the recognition antibodies, respectively. A SP-10 recombinant fusion protein consisting of 125 SP-10 amino acids linked to glutathione transferase was used as a working SP-10 standard. The coefficient of variance for the assay system using the rabbit pAb was in the range of 0.099 to 0.157, and for the assay system using the biotinylated mAb MHS-10 was in the range of 0.081 to 0.084. Employing biotinylated MHS-10 as the recognition antibody, it was found that the native SP-10 molecule had more than one MHS-10 epitope. The concentration of SP-10 in a pool of human sperm extracts was found to be approximately 1% of the total proteins, assayed by both of the recognition antibody systems. The assay system described is useful to monitor the yield of recombinant SP-10 during scale-up production of the SP-10 vaccine.

Monoclonal antibodies for the detection ofRhizomonas Suberifacienscausal agent of corky root of lettuce, with enzyme immunoassays

Monoclonal antibodies (MAbs) were produced to Rhizomonas suberifaciens strain CA1. Initial screening of MAbs was performed with strains CA1 and FL1 of R. suberifaciens and 82 strains of other genera in antibody capture indirect enzyme‐linked immunosorbent assay (ELISA) tests. One MAb (MAb‐Rs 1) reacted with both strains of R. suberifaciens and another (MAb‐Rs 2) only with R. suberifaciens strain CA1. Both MAbs were further screened for cross‐reactivity with 28 strains of R. suberifaciens, four strains of Rhizomonas sp., and 56 strains of unknown bacteria isolated from lettuce, prickly sowthistle and melon roots with symptoms of corky root. All these strains were tested for pathogenicity on lettuce, DNA homology with DNA of R. suberifaciens strain CA1, and cross‐reactivity with both MAbs in indirect antibody capture and indirect double antibody sandwich (DAS) ELISA tests. All strains of R. suberifaciens reacted with MAb‐Rs1 in both indirect ELISA tests, while none of the other strains reacted. In antibody capture indirect ELISA tests, MAb‐Rs2 had affinity to strains of R. suberifaciens from California and New York but not to those from Florida, Wisconsin and one from New York. In indirect DAS ELISA tests, MAb‐Rs2 reacted with all strains of R. suberifaciens. The indirect DAS ELISA tests were more sensitive than the indirect antibody capture tests.

Gravitational diffusion of solar system WIMPs

Gravitational diffusion will cause the phase-space density of solar-bound Earth-crossing weakly interacting massive particles (WIMPs) to equal the phase-space density of the low-velocity free-space WIMPs. This diffusion is generated by encounters with the Earth, Jupiter and Venus. Direct capture by the Earth of bound plus unbound WIMPs is therefore equal to what would be captured were the Earth in free space. Moreover, indirect capture (where WIMPs are first weakly captured into solar orbits and from there truly captured by the Earth) is shown to be negligible. Thus, one may use the free-space formulae for capture, even though the Earth is deep within the potential well of the Sun.

Laboratory diagnosis of Mycoplasma pneumoniae infection. 1. Direct detection of antigen in respiratory exudates by enzyme immunoassay.

Direct and indirect antigen capture enzyme immunoassays (Ag-EIA) have been developed for the detection of Mycoplasma pneumoniae in nasopharyngeal aspirates or sputum from respiratory infection. The sensitivity of the two Ag-EIA were similar, but the indirect method using polyclonal rabbit and guinea-pig antisera was more convenient. The Ag-EIA had a detection limit of 10(4-4.5) colony-forming units/ml of sample. It was specific for M. pneumoniae and gave a low level response with M. genitalium. There were no cross-reactions with 10 other species of mycoplasmas. Tests with a wide range of bacteria and chlamydia group antigen, representing agents sometimes found in the respiratory tract, were also negative. At the current level of development, the Ag-EIA detected about 90% of specimens that were also positive for culture; 43% of specimens from culture-negative--seropositive patients gave a positive result. The overall pattern of results indicated that while antigen detection is a quick and effective substitute for the slow culture method, serological examination for specific IgM antibody is also necessary to give a complete diagnostic coverage.

Direct and indirect capture of weakly interacting massive particles by the earth

Direct and indirect capture of weakly interacting massive particles by the earth

Dissociative recombination of electrons with H2+ in low vibrational states.

Cross sections for the dissociative recombination of electrons and ${\mathrm{H}}_{2}^{+}$ ions having low internal energies have been measured by means of the merged electron-ion beam technique. Narrow resonances associated with indirect capture into high-lying Rydberg states of the neutral molecule have been found. The use of ions with only two vibrational states significantly populated has allowed the high-resolution capability of the merged-beam technique to be clearly demonstrated.

Direct and indirect carrier capture by semiconductor quantum wells

We report theoretical calculations bearing on phonon-assisted carrier capture by semiconductor quantum wells. Direct capture by the quantum well and indirect capture via barrier impurities are considered.

Detection of antibodies and antigens of human parvovirus B19 by enzyme-linked immunosorbent assay.

Acute-phase serum from a patient with aplastic crisis provided sufficient human parvovirus B19 to make a monoclonal antibody against B19 and to develop antigen and immunoglobulin M (IgM) and IgG antibody detection enzyme-linked immunosorbent assays (ELISAs). The indirect capture antibody method was used for all three assays. Antigen was detected in 8 of 29 sera drawn within 2 days of onset of illness from patients with aplastic crisis. These sera had high titers of virus by electron microscopy and DNA hybridization and had no detectable B19 antibody. Antigen was not detected in serum specimens that had low titers of B19 DNA and had B19 antibody. With the IgM ELISA, we detected B19 IgM in over 85% of clinical cases of aplastic crisis and fifth disease and less than 2% of controls. The prevalence of B19 IgG antibodies increased with age. Approximately 2% of children less than 5 years of age and 49% of adults greater than 20 years of age had B19 IgG antibodies. The B19 antibody ELISAs are sensitive and specific tests to detect B19 infections.

Enzyme-linked immunosorbent assay for mumps IgM antibody: Comparison of IgM capture and indirect IgM assay

We have established two enzyme-linked immunosorbent assays (ELISAs) for detection of mumps IgM antibody, i.e., indirect IgM ELISA and IgM capture ELISA, for serodiagnosis of recent mumps infection. In the latter method, peroxidase-conjugated monoclonal antibody to mumps virus was employed. Both methods detected mumps antibody of IgM class only in serum fractions separated by centrifugation through a sucrose density gradient. Optical density values given by both ELISAs were correlated for most sera examined. Indirect IgM ELISA, however, gave a false positive reaction for sera containing both rheumatoid factor and mumps IgG antibody, while giving a false negative reaction for sera containing high titers of mumps IgG antibody. This technique was, therefore, less reliable than IgM capture ELISA. IgM antibody detectable by IgM capture ELISA was present in all patients with mumps by the fifth day of illness and persisted for up to 3 mth in most and up to 5 mth in same cases.