We appreciate the invaluable contributions of the following reviewers during the editing of Vol. 8 Nos. 1–2.

Acknowledgments

We appreciate the invaluable contributions of the following reviewers during the editing of Vol. 8 Nos. 1–2.     

Ecology of the pteridophytes on the southern slopes of Mt. Kilimanjaro – I. Altitudinal distribution

140 taxa of 61 genera in 24 families of pteridophytes were recorded on the southern slopes of Mt. Kilimanjaro. These represent about one third of the entire pteridophyte flora of Tanzania. The families richest in species are the Aspleniaceae, the Adiantaceae, the Dryopteridaceae, the Thelypteridaceae and the Hymenophyllaceae. Due to its luxuriant montane rain forest, which receives a precipitation of up to over 3000 mm, Mt. Kilimanjaro is distinctly richer in pteridophyte species than other volcanoes in East Africa. However, compared with the mountains of the Eastern Arc, the number of pteridophytes on Mt. Kilimanjaro is smaller. This can be explained by the widely destroyed submontane (intermediate) forest rather than by the higher age of the Eastern Arc Mts.The altitudinal distribution of all ferns was investigated in 24 transects. On the southern slopes of Mt. Kilimanjaro they were found in an altitudinal range of 3640 m. Cyclosorus quadrangularis, Azolla nilotica, Azolla africana andMarsilea minuta are restricted to the foothills, while Polystichum wilsonii, Cystopteris nivalis and Asplenium adiantum-nigrum are species found in the highest altitudes.Based on unidimensionally constrained clustering and on the analysis of the lowermost and uppermost occurrence of species, floristic discontinuities within the transects were determined. From these data and from an evaluation of the distribution of ecological groups and life forms, 11 altitudinal zones could be distinguished: a colline zone (–900 m asl), a submontane zone (900–1600 m asl) with lower and upper subzones, a montane zone (1600-2800 m asl) divided into 4 subzones, a subalpine zone (2800–3900 m asl) with lower, middle and upper subzones, and finally a (lower) alpine zone above 3900 m. The highest species numbers were observed in the lower montane forest belt between 1600 and 2000 m altitude. The zonation of ferns found at Mt. Kilimanjaro corresponds well with the vegetational zonation described by other authors using bryophytes as indicators in different parts of the humid tropics.     

Interaction of α-lactalbumin with dimyristoylphosphatidylcholine vesicles. III. Influence of the temperature and of the lipid-to-protein molar ratio on the complex formation

We investigated the interaction between α-lactalbumin and sonicated dimyristoylphosphatidylcholine at pH 4 and different temperatures. (1) At 23°C and lipid-to-protein molar ratios below 170, the interaction results in a disruption of the original vesicles to form smaller complex particles. By the sedimentation velocity method we determined for this particle a molar mass of (1.05 ± 0.16) · 10⁶ g·mol^?1. The lipid-to-protein molar ratio within the complex particle is 70/1, as earlier estimated. It follows that there are approximately 1200 lipid and 17 α-lactalbumin molecules per particle. At molar ratios above 170, α-lactalbumin strongly associates with the vesicles. In this case the vesicle entity remains. The ability of α-lactalbumin to break up the vesicles at this temperature is determined by the number of protein molecules which are required in the complex particle. (2) By means of fluorescence polarization of the lipophilic probe 1,6-diphenyl-1,3,5-hexatriene and energy transfer of the tryptophan groups of the protein to 1,3-(1,1′-dipyrenyl)propane located in the hydrocarbon region of the vesicles, it is shown that with increasing temperature above 25°C, complexes of decreasing internal lipid-to-protein molar ratio are formed. However, by electron microscopy we show that the overall size of these complexes remains approximately the same, i.e., bars with dimensions $\text{70 × 220}\text{A}\text{?}$. A temperature-reversible transformation occurs between these complexes, which cannot be isolated by gel chromatography. In contrast, the complex of molar ratio 70/1 remains stable at lower temperatures.     

A study of the nature of the immediate precursor of the extracellular α-amylase of Bacillus amyloliquefaciens. A reappraisal

1. A defined medium was devised for use in washed-cell experiments with post-exponential-phase cultures of Bacillus amyloliquefaciens. The medium allowed alpha-amylase to be secreted, bacterial concentration to increase and l-[U-(14)C]valine to be incorporated into protein at a linear rate, which was the same as in a post-exponential-phase culture, for up to 6h. 2. Determination of the specific radioactivity of l-[U-(14)C]valine in the medium, the intracellular amino acid pool, the cellular protein and the isolated alpha-amylase, after a 3h incubation of washed cells in the defined medium, showed that at least 76% of the alpha-amylase secreted was synthesized de novo. 3. By isolating the alpha-amylase formed during a 6h incubation in the presence of l-[U-(14)C]valine it was shown that the specific radioactivity of the N-terminal valine, within the limits of experimental error, was the same as that of the total valine residues from the complete alpha-amylase molecule. 4. A consideration of these results in relation to the whole literature on the subject strongly supports the idea that there is no reason to suppose that extracellular alpha-amylase is formed from a high-molecular-weight precursor in B. amyloliquefaciens and closely related organisms with identical characteristics of exoenzyme secretion.     

Molecular characterization of the zerknüllt region of the Antennapedia complex of D. subobscura

We have characterized at the molecular level the zerknüllt (zen) region of the Drosophila subobscura Antennapedia complex. The sequence comparison between D. subobscura and D. melanogaster shows an irregular distribution of the conserved and diverged regions, with the homeobox and a putative activating domain completely conserved. Comparisons of the promoter sequence and pattern of expression of the gene during development suggest that the regulation of zen has been conserved during evolution. The conservation of zen expression in a subpopulation of the polar cells indicates the existence of an important role in such cells. We describe a transitory segmented pattern of expression of zen in both species, suggesting the existence of interactions with a pair rule gene. Some indirect clues indicate that the z2 gene might be absent from the D. subobscura genome. A chromosome walk initiated to reach the proboscipedia gene of D. subobscura reveals that the distance between pb and zen is at least four times the one described for D. melanogaster and for D. pseudoobscura. Finally, we present cytological evidence showing that the ANT-C is inverted in D. subobscura as compared to D. melanogaster.