Euploidie,Aneuploidie und B-Chromosomen beiCaltha palustris L.

Ohne ZusammenfassungMit 21 Textabbildungen.     

Chemical synthesis of tridecanucleoside dodecaphosphate sequence of SV40 DNA

The preparation, by the phosphotriester approach, of d[C-T-A-T-T-C-C-A-G-A-A-G-T] from one tetranucleoside triphosphate and three trinucleoside diphosphate blocks is described. The use of the o-dibromomethylbenzoyl (DBMB) protecting group in oligodeoxyribonucleotide synthesis is described for the first time. Internucleotide linkages are protected by o-chlorophenyl groups which are finally removed by treatment with the N1, N1, N3, N3-tetramethylguanidinium salt of syn-4-nitrobenzaldoxime. The first phosphorylation step (leading to phosphodiester intermediates) is carried out by treatment with o-chlorophenyl phosphorodi-(1,2,4-triazolide) followed by treatment with water and triethylamine. 1-Mesitylenesulphonyl-3-nitro-1,2,4-triazole (MSNT) is used as the activating agent in the second phosphorylation step in which 5'-protected mono- and di-nucleotides are condensed with nucleoside building blocks containing unprotected 3'-hydroxy functions.     

Effects of essential divalent metals on carcinogenicity and metabolism of nickel and cadmium

Interactions between the physiologically essential metals calcium, magnesium, and zinc and the carcinogenic metals nickel and cadmium were investigated to help elucidate the mechanisms of action of the carcinogenic metals. Bioassay studies revealed several significant findings, including: (1) the ability of magnesium and calcium to inhibit nickel-induced elevation of pulmonary adenoma incidence in strain A mice; (2) the ability of magnesium, but not of calcium, to prevent cadmium-induced subcutaneous sarcoma formation; and (3) the ability of magnesium, but not of calcium, to inhibit nickel-induced muscle tumor formation. Biochemical studies indicated a direct relationship between the antitumorigenic potential of magnesium and the capacity of this metal to: (1) inhibit nickel and cadmium uptake by the target tissues in vivo; (2) inhibit nickel-induced disturbances in DNA synthesis in vivo; (3) inhibit nuclear and cytosolic uptake of nickel by the target tissue cells in vivo; and (4) inhibit nickel and cadmium binding to DNA in vitro. Calcium, which in most cases did not prevent carcinogenesis, had no consistent influence on the uptake of carcinogenic metals or their biochemical effects in the target tissues. Magnesium and zinc, but not calcium, were also found to attenuate the acute toxic effects of nickel, indicating a possible correlation between prevention of acute effects and reduction in tumorigenicity. Zinc, which antagonizes cadmium tumorigenicity in the rat testis, was found to reduce markedly cadmium uptake into isolated testicular interstitial cells. Also, zinc was found to inhibit strongly cadmium binding to DNA in vitro.     

Calymperes (Musci: Calymperaceae): World ranges,implications for patterns of historical dispersion and speciation,and comments on phylogeny

Refinements in the taxonomy of the genus Calymperes (Musci: Calymperaceae) allow increasingly accurate estimates of the total number of species worldwide and new assessments of world ranges of the species. Instead of the 272 correct names of Calymperes listed in Volume 1 of Index Muscorum, the world total of “good” species now appears to be in the range of 30 to 40, and contrary to the high degree of narrow endemism implied from the compilation of Index Muscorum, many species of Calymperes have broad ranges in the paleo- or neotropics. A few species, including C. afzelii, C. erosum, C. palisotii, C. lonchophyllum, and C. tenerum, are pantropical. World ranges of species of Calymperes are mapped and implications for historical patterns of dispersal and speciation are discussed. Suites of endemic species and species groups in the neotropics differ from those in the paleotropics, demonstrating different ancestries, a long period of geographic separation, and independent evolution in two fundamentally different environments. It is suggested that Calymperes shares close phylogenetic relationship with limbate Syrrhopodon.     

Nitrogen mineralization ofSesbania sesban used as green manure for lowland rice in Sri Lanka

Sesbania sesban was evaluated as green manure crop for lowland rice in the Dry Zone of Sri Lanka. The legume was grown during a fallow period before lowland rice (Oryza sativa) and ploughed under just before transplanting. Weight loss and nitrogen content in litterbags containing leaves, stems and roots of the legume were monitored. Comparisons were made between rice yields from 20 m² plots after green manuring in combination with different nitrogen fertilizer levels (0, 2.4, 4.8 and 7.2 gm⁻²) and nitrogen fertilizer (9.6 gm⁻²) alone. Above-ground biomass ofS. sesban was 440 gm⁻² (dry wt) when ploughed under after 84 days growth. N-content in leaves, stems and roots was 3.76%, 0.41% and 0.73%, respectively. This gave a N-input fromS. sesban of 9.2 gm⁻² (8.3 g from above-ground parts and 0.9 g from roots). The corresponding K and P inputs were 7.3 and 0.6 gm⁻² respectively. The nitrogen rich leaves, which contained 88% of the nitrogen in the above-ground parts, decomposed and released its nitrogen much more rapidly than the stems and roots. After only four days the leaves had released 5.3 g Nm⁻² and after 14 days they had released 6.4 g Nm⁻². The highest rice yield (505 gm⁻²) was obtained usingS. sesban and 4.8 gm⁻² of N-fertilizer. The yields with only N-fertilizer or onlyS. sesban were 442 gm⁻² and 396 gm⁻², respectively. Due to the rapid decomposition of the nitrogen rich leaves,S. sesban did not behave as a slow release fertilizer. Thus, it is not necessary to apply nitrogen fertilizers as a basal dose.     

The role of kinesin and other soluble factors in organelle movement along microtubules

Kinesin is a force-generating ATPase that drives the sliding movement of microtubules on glass coverslips and the movement of plastic beads along microtubules. Although kinesin is suspected to participate in microtubule-based organelle transport, the exact role it plays in this process is unclear. To address this question, we have developed a quantitative assay that allows us to determine the ability of soluble factors to promote organelle movement. Salt-washed organelles from squid axoplasm exhibited a nearly undetectable level of movement on purified microtubules. Their frequency of movement could be increased greater than 20-fold by the addition of a high speed axoplasmic supernatant. Immunoadsorption of kinesin from this supernatant decreased the frequency of organelle movement by more than 70%; organelle movements in both directions were markedly reduced. Surprisingly, antibody purified kinesin did not promote organelle movement either by itself or when it was added back to the kinesin-depleted supernatant. This result suggested that other soluble factors necessary for organelle movement were removed along with kinesin during immunoadsorption of the supernatant. A high level of organelle motor activity was recovered in a high salt eluate of the immunoadsorbent that contained only little kinesin. On the basis of these results we propose that organelle movement on microtubules involves other soluble axoplasmic factors in addition to kinesin.