SUMMARYA panel of eight neutralizing monoclonal antibodies (MAbs) against the fusion (F) protein of Newcastle disease virus (NDV) has been shown to locate a major antigenic site on the basis of competitive binding assay and additivity index studies. Five epitopes (A 1 to AS) have been located within this site on the F protein of the Beaudette C strain of NDV on the basis of cross-resistance plaque assays of MAb-resistant mutants raised against these MAbs. Epitopes A1, A4 and A5 are distinct; epitope A2 partially overlaps epitope A3. Nucleotide sequence analysis of the F genes of MAbresistant mutants showed that each predicted single amino acid substitutions ranging from amino acid residues 157 to 171 for epitope A4 and at residues 72, 78, 79 and 343 for epitopes A 1, A2, A3 and A5 respectively. These locations indicate that both the F 1 and F2 fragments are involved in the formation of a single antigenic site and suggest the involvement of extensive protein folding in the active form of this F protein.
SUMMARYA highly reproducible monoclonal antibody (Mab) blocking ELISA (B-ELISA) has been developed and evaluated for the detection of NDV-specific antibodies. The Mab utilised is specific for a conserved PMV-1 serotype-specific epitope, as demonstrated by the indirect immunoperoxidase test. It reacted with all strains representing different serogroups within the PMV-1 serotype, but not with any strain belonging to other PMV serotypes.Sensitivity and specificity of the B-ELISA were compared with the haemagglutination inhibition test (HI). Blocking and HI antibodies were detected in sera of chickens 8 days post-experimental infection. The B-ELISA proved consistently more sensitive than the HI test. In another survey, 62 sera from experimentally vaccinated chickens were tested; 95.2% proved positive by B-ELISA, 85.5% by indirect ELISA and 74% by HI test. When 504 field sera from vaccinated chickens and turkeys were tested, 98% were positive by B-ELJSA, and 69% by HI. The specificity was evaluated by testing 1066 samples from NDV-free flocks, all of which proved negative by both methods. Other advantages of the B-ELISA include easy standardization and quality control, and ability to test sera from any species (including exotic or wild birds as well as mammals). The use of low dilution serum or egg-yolk samples makes the test quick and easy to perform and suitable for large-scale screening.
Examples of a variety of approaches for studying the mechanism and regulation of cellulose biosynthesis are presented. Attempts to demonstrate conclusively a cellulose synthase activity using membrane preparations derived from higher plants have not been successful; the predominant UDP-glucose: /3-glucan-/3-glucosyltransferase detected in these preparations is a /3-(l->3)-glucan synthase that is dependent upon Ca2+ and a /3-glucobiose, such as laminaribiose or cellobiose, for activity. Xyloglucan glucosyltransferase activity is detected in all plant preparations examined and, in cotton fibres, the activity of this enzyme correlates well with the level of xyloglucan found in the fibre. Low activity for a Mg2+-dependent /3-(l-»4)-glucan synthase is found in extracts from soy beans and mung beans, but not cotton fibres; this enzyme could represent either a dissociated form of xyloglucan glucosyltransferase or a partially latent form of cellulose synthase. In vitro translation of RNA from developing cotton fibres shows notable increases in the level of several relatively abundant translatable mRNAs associated with the time of onset of secondary-wall cellulose synthesis. In order to determine whether these apparent changes in gene expression represent enhanced expression of specific genes required for cellulose synthesis, several strategies are being developed for identification of specific polypeptides required for this process. One strategy involves the successful development of a technique for detection of glucan synthase activity in acrylamide gels, a technique that should prove useful for characterization of the polypeptide composition of such enzymes. We have also synthesized a photoaffinity analogue of 2,6-dichlorobenzonitrile (DCB), a potent and specific inhibitor of cellulose synthesis. The analogue is also an effective inhibitor in vivo, and upon ultraviolet irradiation of extracts in the presence of the radioactive analogue, we observe a relatively specific labelling of a polypeptide of 18 X 103 Mr. Finally, we have studied the spatial regulation and structural requirements for cellulose synthesis in internode cells of the alga Chara corallina. Cellulose deposition in vivo shows spatial localization, which correlates with acid and base bands along the cell. Using internodes perfused with solutions containing UDP-[14C]glucose and subsequently ligated, we were able to demonstrate synthesis of a highly insoluble cell-wall-localized glucan, thus offering hope that Chara can be developed as another useful system for studying the mechanism and regulation of cellulose synthesis. I N T R O D U C T I O NSince microfibrillar cellulose is a major structural component of the cell walls of higher plants, and many algae and fungi, regulation of the extent and pattern of deposition of this polymer must certainly be involved in the overall regulation of growth and development in these organisms. Thus, it is regrettable that biochemical studies on the mechanism of synthesis of cellulose have proven so difficult; our lack o...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.