We show that most isolates of influenza A induce filamentous changes in infected cells in contrast to A/WSN/33 and A/PR8/34 strains which have undergone extensive laboratory passage and are mouse-adapted. Using reverse genetics, we created recombinant viruses in the naturally filamentous genetic background of A/Victoria/3/75 and established that this property is regulated by the M1 protein sequence, but that the phenotype is complex and several residues are involved. The filamentous phenotype was lost when the amino acid at position 41 was switched from A to V, at the same time, this recombinant virus also became insensitive to the antibody 14C2. On the other hand, the filamentous phenotype could be fully transferred to a virus containing RNA segment 7 of the A/WSN/33 virus by a combination of three mutations in both the amino and carboxy regions of the M1 protein. This observation suggests that an interaction among these regions of M1 may occur during assembly.

SUMMARYInteraction between the pollen grain, pollen tube and the stigma surface has been studied in five species regarded as possessing dry stigma surfaces; Brassica oleracea L., Arabidopsis thaliana (L.), Heynh, Papaver rhoeas L., Cosmos bipinnatus Cav. and Helianthus annuus L.In B. oteracea and A. thaliana, stigmatic response to pollination includes events in the papillar cytoplasm and changes to the stigmatic surface beneath the grain. In particular a specialized outer element of the cell wall expands prior to pollen tube penetration. The pollen tube, which enters through a ' foot' of pollen coating, grows in a space generated between an inner and the outer element of the wall and extends to the base of the papilla where it enters the middle lamellae of the subjacent cell layer. However, in A. thaliana tubes frequently were seen to penetrate all components of the stigmatic cell wall, an event only previously recorded in immature stigmas of B. oleracea. In self pollinations of self-incompatible B. oleracea involving strong S (incompatibility) alleles no changes take place in the papillar cell wall.In P. rhoeas the stigmatic surface responds to self and cross pollination by the secretion of electron-lucent material beneath the cuticle, causing it to become detached from the outer surface of the stigmatic cell wall. The pollen tubes then penetrate the cuticle and grow towards the base of the papilla in the space thus generated. The tubes continue to grow intercellularly in the transmitting tissue which lies horizontally in rays beneath the papillae.In members of the Compositae, C bipinnatus and H. annuus, both stigma and pollen respond to pollination by producing copious quantities of an electron-opaque matrix, which frequently causes individual papillae to adhere together. Pollen tubes, which are formed following both compatible and incompatible intraspecific pollinations, grow into this matrix and toward the base of the papillae. There, in common with the other plants studied, they grow intercellularly and enter the transmitting tissue of the style.These findings are discussed in the light of current views of the mechanisms operating during angiosperm pollination and of the significance of the stigmatic response to the functioning of self-incompatibility mechanisms.

A simple solution-based (1)H-NMR method for measurement of anomeric composition of lactose has been established. The solution β/α ratio at the time of drying is mirrored in the composition of the resulting solid amorphous material. In order to produce a consistent anomer composition within spray and freeze dried amorphous lactose, the standing time for the feed solution should be greater than 4 h, such that the most dynamic region of the mutarotation profile has been exceeded. If the amorphous material has been formed from a solution that has not been allowed to equilibrate for 4 h, the resulting solid will continue to undergo mutarotation if trace amounts of moisture are present, until the anomeric β/α ratio slowly approaches 1.7.

SUMMARYWhen the dehydrated pollen grain of Brassica oleracea L. alights on a receptive stigma the pollen coat flows out from the exine to form an appresoria-like ' foot' and, within a matter of some 30 min, gross ultrastructural changes become visible both within the protoplast and in the foot itself. These changes are interpreted as reflecting the limited movement of water, and presumably other materials, from the stigma to the grain. The compatible pollen grain then continues to take up water, whilst undergoing other cytoplasmic changes and eventually producing the pollen tube. The tube grows from the colpus towards the point of contact with the stigma, beneath which the outer layer of the papillar wall has become more loosely packed. The pollen tube enters the wall at this point and, as a consequence of its rapid extension, the grain is frequently lifted away from the papilla. The tube then grows between two layers of the pectocellulosic papillar wall into the stigmatic parenchyma, where it follows an intercellular route. These events are discussed in terms of current views of the relationship between male and female cells at these early stages of the pollen stigma interaction.

An in vitro bioassay has been developed to explore the role of the pollen coating in the pollen/stigma interaction in Brassica oleracea. In the assay, coating is removed from pollen grains, supplemented with protein fractions isolated from coatings of different S (self incompatibility) haplotypes, and then—using micromanipulation—interposed between individual pollen grains and the stigmatic surface. Normally, the coating used is of the same haplotype as the pollen in the experiment—thus constituting an ‘extension’ of its own coat—but carrying the supplemented protein fractions. Initial experiments confirmed preliminary data that the pollen coating contained the male determinant of self incompatibility (SI); not only did the addition of ‘self’ coating (i.e. that with the same S‐haplotype as the stigma) prevent the success of a compatible cross pollination, but a ‘cross’ coating (i.e. that with a different S‐haplotype from the stigma) could induce the germination and growth of self pollen. Protein supplementation experiments demonstrated that the pollen‐held determinant is contained within the water soluble component of the pollen coat, while further analysis revealed that the active molecular species possesses an Mr10 kDa. More extensive fractionation by gel filtration and reverse phase HPLC was used to isolate a family of basic, cysteine‐rich proteins (PCP‐A: Pollen Coat Proteins‐class A)—one of which is known to bind to stigmatically‐expressed components of the S‐locus in Brassica. Introduction of the PCP‐A protein fraction into the bioassay confirmed the male determinant of SI as a protein, and probably a member of the PCP‐A protein family.