BackgroundBoth male and female pigeons have the ability to produce a nutrient solution in their crop for the nourishment of their young. The production of the nutrient solution has been likened to lactation in mammals, and hence the product has been called pigeon 'milk'. It has been shown that pigeon 'milk' is essential for growth and development of the pigeon squab, and without it they fail to thrive. Studies have investigated the nutritional value of pigeon 'milk' but very little else is known about what it is or how it is produced. This study aimed to gain insight into the process by studying gene expression in the 'lactating' crop.ResultsMacroscopic comparison of 'lactating' and non-'lactating' crop reveals that the 'lactating' crop is enlarged and thickened with two very obvious lateral lobes that contain discrete rice-shaped pellets of pigeon 'milk'. This was characterised histologically by an increase in the number and depth of rete pegs extending from the basal layer of the epithelium to the lamina propria, and extensive proliferation and folding of the germinal layer into the superficial epithelium. A global gene expression profile comparison between 'lactating' crop and non-'lactating' crop showed that 542 genes are up-regulated in the 'lactating' crop, and 639 genes are down-regulated. Pathway analysis revealed that genes up-regulated in 'lactating' crop were involved in the proliferation of melanocytes, extracellular matrix-receptor interaction, the adherens junction and the wingless (wnt) signalling pathway. Gene ontology analysis showed that antioxidant response and microtubule transport were enriched in 'lactating' crop.ConclusionsThere is a hyperplastic response in the pigeon crop epithelium during 'lactation' that leads to localised cellular stress and expression of antioxidant protein-encoding genes. The differentiated, cornified cells that form the pigeon 'milk' are of keratinocyte lineage and contain triglycerides that are likely endocytosed as very low density lipoprotein (VLDL) and repackaged as triglyceride in vesicles that are transported intracellularly by microtubules. This mechanism is an interesting example of the evolution of a system with analogies to mammalian lactation, as pigeon 'milk' fulfils a similar function to mammalian milk, but is produced by a different mechanism.

Koi herpesvirus (KHV) is the aetiological agent of an emerging disease (KHVD) associated with mass mortalities in koi and common carp and reported from at least 30 countries. We report the first isolation of KHV from koi and common carp in Indonesia and initial characterization of the isolates. Clinical signs, histopathology and virion morphology are similar to those of isolates from other countries. Phylogenetic analyses using the thymidine kinase gene amplified from each isolate and from carp tissue samples collected from KHVD outbreaks throughout Indonesia indicated that the Indonesian isolates are more closely related to the Asian than the European KHV lineage. Sequence analysis of two other variable regions between ORF29 and ORF31 (marker I) and near the start of ORF 133 (marker II) indicated that all Indonesian isolates displayed a marker I allele (I(++)) previously identified only in isolates of the Asian lineage. However, in the marker II region, all Indonesian isolates displayed the II(-) allele, which has been reported previously only amongst isolates of the European lineage, and nine of these displayed a mixed genotype (II(+)II(-)). The I(++)II(-) genotype has not been reported previously and appears to represent a new intermediate lineage that may have emerged in Indonesia.

The results suggest that SSP+ could be used for platelet storage for up to 9 days. However, the preparation of platelets in the additive requires some optimization. In vivo studies are required to confirm these in vitro results.