Widespread occurrence of AP in amyloidotic tissues. An immunohistochemical observation

Plasma (P)-component of amyloid (AP or SAP), while not an integral part of the amyloid fibril, has been considered to be intimately associated with virtually every different type of amyloid. In the present study, we evaluated the distribution of AP in the organs frequently involved in two forms of human systemic amyloidosis (AA and AF) and in mouse AA amyloidosis, by use of immunohistochemistry with anti-AP. Although the amyloid deposits generally showed moderate reactions with anti-AP, they were not always clearly distinguished from the surrounding non-amyloid tissue elements which often stained as well. The basement membrane often showed even stronger reaction to anti-AP than the adjacent amyloid deposits, and liver sections demonstrated such a high overall reaction to anti-AP that the anti-AP reaction on the amyloid deposits was often obscurred. The present results suggest that the binding between AP and the amyloid fibril may not be monospecific, that AP by this technique occurs rather widely throughout the body, and therefore that anti-AP may not be considered as specific a marker for amyloid deposits in immunohistochemical and perhaps other studies as well.     

Faster evolution of highly conserved DNA in tropical plants

A faster rate of nuclear DNA evolution has recently been found for plants occupying warmer low latitudes relative to those in cooler high latitudes. That earlier study by our research group compared substitution rates within the variable internal transcribed spacer (ITS) region of the ribosomal gene complex amongst 45 congeneric species pairs, each member of which differed in their latitudinal distributions. To determine whether this rate differential might also occur within highly conserved DNA, we sequenced the 18S ribosomal gene in the same 45 pairs of plants. We found that the rate of evolution in 18S was 51% faster in the tropical plant species relative to their temperate sisters and that the substitution rate in 18S correlated positively with that in the more variable ITS. This result, with a gene coding for ribosomal structure, suggests that climatic influences on evolution extend to functionally important regions of the genome.     

Effect of temperature on growth of guanidine-resistant mutants of poliovirus

Guanidine-resistant (gr) mutants of poliovirus were previously categorized into four groups by electrophoretic properties and peptide maps of nonstructural virus protein 2C. Growth of mutants in the presence of guanidine depends upon temperature of incubation. The four groups of gr variants respond differently to temperature when guanidine is included in the culture medium. The data suggest clustering of gr mutations at several sites in the guanidine locus.     

Isolation and analysis of monoclonal antibodies against various gangliosides

Female BALB/c mice were immunized with human melanoma (Mewo) cells containing ganglioside GD3 as a surface antigen. Immune splenocytes were fused with syngeneic P3-X63.Ag 8 myeloma cells. Antibodies produced by hybrid clones were analyzed by solid phase immunoassay. B, C, D and Q clones producing antibodies against Raja clavata brain gangliosides were obtained. Monoclonal B and C antibodies bound monosialogangliosides. Monoclonal D antibody bound a number of gangliosides but reacted predominantly with GD1a. Monoclonal Q antibody reacted selectively with GQ1c. It is assumed that ganglioside GQ1c is expressed on the melanoma cell surface and may be found only in the early stage of ontogenesis of high vertebrates.     

Variation in serotiny of three Banksia species along a climatic gradient

The degree of serotiny (i.e. the proportion of follicles remaining closed in each year's crop of cones since the last fire) was measured in Bank-sia attenuata, B. menziesii and B. prionotes at five sites along a climatic gradient extending 500 km north of Perth, Western Australia. The decrease in annual rainfall and increase in average temperature along the gradient paralleled a decrease in plant height and an increase in the degree of serotiny of all species. Extreme serotiny was recorded in the scrub-heath at the xeric end of the gradient whereas two species were essentially non-serotinous in the low woodland at the most mesic site. It is concluded that degree of serotiny is related to the fire characteristics of the site which depend on plant height. In xeric scrub-heath, the entire canopies of the Banksia spp. are consumed by fire which promotes massive release of seed. This facilitates recruitment in an otherwise unpredictable and unreliable seedbed. In mesic woodland, where cones rarely come into contact With flames, seeds are released spontaneously and site conditions are more conducive to recruitment in the inter-fire period.     

Solid-phase synthesis of polymyxin B1 and analogues via a safety-catch approach.

As part of a program towards the development of novel antibiotics, a convenient method for solid-phase synthesis of the cyclic cationic peptide polymyxin B1 and analogues thereof is described. The methodology, based on cleavage-by-cyclization using Kenner's safety-catch linker, yields crude products with purities ranging from 37-67%. Antibacterial assays revealed that analogues 23-26, in which the (S)-6-methyloctanoic acid moiety is replaced with shorter acyl chains, exhibit distinct antimicrobial activity. The results suggest that the length of the acyl chain is rather critical for antimicrobial activity. On the other hand, substitution of the hydrophobic ring-segment D-Phe-6/Leu-7 in polymyxin B1 with dipeptide mimics (i.e. analogues 27-33) resulted in almost complete loss of antimicrobial activity.