The role a botanical institute can play in the conservation of the terrestrial biodiversity in a developing country

The need to integratein situ conservation into the planning process is outlined, and the importance of vegetation survey to determine conservation priorities and to identify areas suitable forin situ conservation is stressed. A case is presented, drawing on experience gained in Zimbabwe, of how a botanical institute can become an integral part of biological conservation. The institute should consist of a herbarium, a botanical garden, a gene bank and a vegetation survey unit. The function of each section, how they interlink, and how they can be integrated are discussed.     

Formation of septa in the bulbus cordis of a turtle and a lizard

The epithelium lining the intrahepatic bile ducts of normal adult mice consists of a single layer of cuboidal or low columnar cells and has ultrastructure comparable to that described previously (Rouiller and Jézéquel, '65). Some of the epithelial cells, however, exhibit such particular features as dilatation of granular endoplasmic reticulum cisternae, polysome formation of ribosomes and the presence of active forms of the Golgi apparatus, numerous lysosome-like bodies and apical projections and blebs. Postnatal cholecystectomy does not induce any qualitative changes in the epithelial fine structure, but results in a significant increase in number of the particular structures mentioned. Therefore, the cholecystectomy is thought to stimulate the secretory activity of the epithelial cells, and such stimulation appears due to the absence of a possible activity of epithelial secretion in the gallbladder.     

What Can We Learn from the Evolution of Protein-Ligand Interactions to Aid the Design of New Therapeutics?

Efforts to increase affinity in the design of new therapeutic molecules have tended to lead to greater lipophilicity, a factor that is generally agreed to be contributing to the low success rate of new drug candidates. Our aim is to provide a structural perspective to the study of lipophilic efficiency and to compare molecular interactions created over evolutionary time with those designed by humans. We show that natural complexes typically engage in more polar contacts than synthetic molecules bound to proteins. The synthetic molecules also have a higher proportion of unmatched heteroatoms at the interface than the natural sets. These observations suggest that there are lessons to be learnt from Nature, which could help us to improve the characteristics of man-made molecules. In particular, it is possible to increase the density of polar contacts without increasing lipophilicity and this is best achieved early in discovery while molecules remain relatively small.     

Genetic interaction between Non-MHC T- and B-cell alloantigens in response to rous sarcomas in chickens

Chickens of Regional Poultry Research Laboratory (RPRL) inbred line 6₃ regress sarcomas induced by Bryan high-titer Rous sarcoma virus to a greater extent than chickens of line RPRL 100, although these lines are identical for the major histocompatibility B complex. They differ, however, at three independent autosomal loci: Ly-4 and Th-1 determine the surface alloantigens of partly overlapping subsets of T lymphocytes, and Bu-1 determines a surface alloantigen of B lymphocytes. The association of genotypes at these loci with quantitative variation in their ability to regress Rous sarcomas was tested in segregating F₄ generation progeny derived from crosses of lines 100 and 6₃. The Ly-4 and Bu-1 genotypes showed association with Rous sarcoma regression, but the Th-1 genotype did not. Chickens of the Ly-4 ^a/Ly-4 ^a, Bu-1 ^b/Bu-1 ^b and Ly-4 ^b/Ly-4 ^b, Bu-1 ^a/Bu-1 ^a genotypes had a significantly higher regressor ability than the other two double homozygous genotypes. These results indicate that higher regression is associated with (1) interaction between the Ly-4 and Bu-1 loci, and (2) complementation between either the line 6 Ly-4 ^a allele and the line 100 Bu-1 ^b allele, or the line 100 Ly-4 ^b allele and the line 6 Bu-1 ^a allele.     

Mutagenic activity of nine N,N-disubstituted hydrazines in the Salmonella/mammalian microsome assay.

The mutagenic activity of N,N-dimethyl-, N,N-diethyl-, N,N-dibutyl-, N,N-diisobutyl-, N,N-di(p-tolyl)-, N-ethyl-N-phenyl-, N,N-dibenzyl-, N,N-diphenyl- and N,N-diisopropylhydrazine was examined in the Salmonella/mammalian microsome assay using the strains TA1535, TA1537, TA97, TA98, TA100, TA102 and TA1530. All nine hydrazines were mutagenic in at least one tester strain, although of borderline significance for some of the compounds. The mutagenic potencies of the hydrazines varied 2-3 orders of magnitude, from very weak to moderate mutagenic activity. In general, the addition of S9 resulted in a lowering of the mutagenic activity and a lowering of the toxic properties of the hydrazines. The test results were relatively difficult to evaluate due to toxic effects of many of the test compounds on the test bacteria which may have resulted in an underestimation of the mutagenic potencies of some of the compounds. The pattern of mutagenic activity of the hydrazines in the different tester strains indicates that more than one mechanism of action may be involved in the mutagenicity.