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A neutral glycan containing L-rhamnose and 2-acetamido-2-deoxy-D-galactose is one of two polymers present in the lipopolysaccharide extract from the reference strain for Serratia marcescens serogroup O23. The glycan, which has the disaccharide repeating-unit shown, shares structural features with polymers from several other O serogroups. ----4)-alpha-L-Rhap-(1----4)-beta-D-GalpNAc-(1----.

Microdialysis sampling was used to measure the release of oxytocin (OXY) and monoamine and amino acid transmitters from the region of the medial preoptic area (MPOA) and the bed nucleus of the stria terminalis (BNST) during parturition and suckling in sheep. Results showed that OXY and gamma-aminobutyric acid release increased in both the MPOA and BNST during parturition and suckling. Noradrenaline (NA) release increased in both structures during parturition but not during suckling. Dopamine (DA) release increased in the MPOA and decreased in the BNST during both parturition and suckling. Aspartate release increased in the MPOA during parturition, and the BNST during suckling, and glutamate release increased in the MPOA and BNST at parturition and only in the BNST during suckling. No changes in the release of serotonin or taurine occurred in these structures during parturition or suckling. In a further experiment on 6 estrogen-primed sheep, OXY (10 micrograms/ml) was infused into the MPOA via bilaterally placed microdialysis probes. This treatment inhibited rejection behavior towards lambs, but did not activate positive maternal responses. These OXY infusions also stimulated release of NA. These results show that complex patterns of neurochemical release occur in two closely related areas of the brain, the BNST and MPOA, during parturition when maternal behavior is stimulated. However, while these patterns of release are similar in the two structures, particularly at birth when maternal behavior is stimulated, they are not identical during labor contractions and suckling. The release of oxytocin within the MPOA during parturition may be important for stimulating a reduction in aggression towards lambs, although this action might be mediated via the effect of OXY on NA release.

In addition to a neutral glycan, lipopolysaccharide extracts from the reference strain for Serratia marcescens serogroup O22 contain an acidic polymer which probably defines the serogroup and is of microcapsular origin. The polymer is doubly branched with a heptasaccharide repeating unit and a galactan backbone. By means of spectroscopic and degradative studies, the structure of the repeating unit was established as that shown. [formula: see text]

Serogroups O2 and O3 of Serratia marcescens are differentiated by acidic glycans present in the aqueous phase when lipopolysaccharides are extracted from the reference strains by the aqueous-phenol method. The phenolic phases of these extracts from both strains also contain lipopolysaccharides, from which the same neutral glycan is released on milk acid hydrolysis. The neutral glycan has the disaccharide repeating-unit shown, and accounts for the cross-reactions between the two serogroups and also with serogroup O21: --> 4)-alpha-D-GlcpNAc-(1-->4)-beta-D-ManpNAc-(1--.