Background: The endometrium is commonly infected with bacteria leading to severe disease of the uterus in cattle and humans. The endometrial epithelium is the first line of defence for this mucosal surface against bacteria and Toll-like receptors (TLRs) are a critical component of the innate immune system for detection of pathogen associated molecular patterns (PAMPs). Antimicrobial peptides, acute phase proteins and Mucin-1 (MUC-1) also provide non-specific defences against microbes on mucosal surfaces. The present study examined the expression of innate immune defences in the bovine endometrium and tested the hypothesis that endometrial epithelial cells express functional receptors of the TLR family and the non-specific effector molecules for defence against bacteria.

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Cycloaddition of a-nitrosostyrene (1 a) to several substituted styrenes is shown to give 3-phenyl-5,6dihydro-4H-l,2-oxazines (2) in moderate yield. Reactions with 4-nitro-a-nitrosostyrene (1 b) give better yields of the corresponding adducts (3). The preferred conformations of the adducts are deduced from their n.m.r. spectra. The observed regio-and stereo-selectivities of the additions are interpreted in terms of a one-step addition in which the olefins act as the donor components.The first example of a formal 1,3-dipolar addition of a vinyl nitroso compound is provided by the formation of the nitrone (5) as a minor product of the reaction of a-nitrosostyrene with 2-methoxypropene. The relative yield of this nitrone is not increased by the change to a more polar solvent, nor by the use of tc-bromoacetophenone anti-oxime in place of the usual syn isomer as the precursor of a-nitrosostyrene. It is suggested that this, and other minor products (4) isolated from the cycloadditions, may be formed because of steric inhibition of the usual Diels-Alder-type process.* Preliminary experiments were carried out by Dr. G. M. Iskander.