Computation of relaxation matrix elements from incomplete NOESY data sets

Summary The structural determination of biological molecules in solution by NMR relies on the determination of a set of interatomic distances obtained by measurement of intramolecular nuclear Overhauser effects (NOE). It is shown in this paper that it is possible to obtain the accurate relaxation rate (and hence the interatomic distance) from the direct measurement of a single NOE signal. The precise analysis of a NOESY peak evolution with respect to the mixing time allows the evaluation of the relaxation parameters for the pair of spins under consideration. This is done without any assumption on the relaxation of unmeasured spins, or on the movement of the molecule. The theoretical basis of this method is presented. In order to evaluate the proposed method, a simulated case on the protein BPTI is studied, which shows that the method performs very well even in the case of noisy data sets.     

Body size, age and reproduction in the leopard toad, Bufo pardalis

Data on the relationships between body size and age were obtained for a sample of leopard toads Bufo pardalis from a breeding population of this species from the Cape Peninsula, South Africa. Age was determined by counting the number of lines of arrested growth in histological sections of a digit clipped from each individual. In males there was a positive, but weak, correlation (explaining only 18% of the variance) between body size and age, and in females no correlation at all existed between these two variables. Males which were successful in obtaining matings were not older than unsuccessful males. Age of males at the breeding site ranged from one to three years, whereas females ranged from two to six years old. This represents both the earliest age of reproduction, as well as the greatest difference in longevity between the sexes, documented for an anuran species.     

Minimal growth factor requirements of human fetal kidney in serum- and glucose-free culture.

The addition of insulin plus transferrin to Leibovitz's L-15 medium was previously shown to restore important cellular functions in a serum-free system developed in our laboratory for human fetal kidney explants. The objective of the present study was to compare the effectiveness of this insulin plus transferrin combination with one used in other in vitro systems whereby serum is substituted by a mixture of five hormones (insulin, transferrin, hydrocortisone, triiodothyronine and prostaglandin E1). In fetal kidney it was found that the combination of insulin plus transferrin was as effective as the five-hormone mixture on DNA synthesis after 5 days of culture and was even more effective in younger fetuses (10-13 weeks) compared with older fetuses (16-19 weeks). However, protein synthesis was more sensitive to the five-hormone combination. Selective deletion of individual hormones showed that insulin is the essential factor for the growth of cultured kidney explants. Differentiation of brush border membranes in nephrons, as evaluated by alkaline phosphatase and gamma-glutamyl-transferase activities, was not significantly modified by either of the two combinations. The present results indicate that insulin plus transferrin represents the optimizing condition for our culture model. The response to supplements varies according to fetal age and possibly to tissue proliferation states and/or cell type.     

Conversion of large heterologies in Streptococcus pneumoniae

In genetic transformation, long deletions dramatically increase the frequency of wild-type recombinants in 2-point crosses. In 3-point crosses in which the deletion was localized between 2 point mutations we demonstrated that this hyper-recombination was the result of genetic conversion extending over several scores of bases outside the deletion. As this conversion did not require an active DNA polymerase A gene, it was proposed that the mechanism of conversion involves breakage and ligation between DNA molecules. A similar hyper-recombination was observed when donor DNA carried an insertion. These results suggest that long heterologies participated in recombination so that surrounding homologous regions are almost completely paired and that these long heterologies are converted. It appears that it is a process that evolved to correct errors of replication which lead to long deletions and which are not eliminated by other systems.     

Assignment by in situ hybridization of a fibroblast growth factor receptor gene to human chromosome band 10q26

Summary A 2.3-kb cDNA probe for the human bek fibroblast growth factor receptor was used to determine the chromosomal localization of the corresponding gene by in situ hybridization. The results show that this gene, a form of which is amplified in some poorly differentiated stomach cancers, is localized on chromosome region 10q26. The two previously identified fibroblast growth factor receptor genes are thus not on the same chromosome, as the related fig (fms-like gene) fibrovblast growth factor receptor gene has previously been mapped to human chromosome region 8p12.     

Transformation of distinct mycobacterial species by shuttle vectors derived from theMycobacterium fortuitum pAL5000 plasmid

Mycobacterium tuberculosis H37Ra,M. smegmatisATCC 607,M. smegmatis MC²155,M. aurum A +,M. aurum A11, and one representative strain ofM. flavescens were transformed by electroporation with plasmid pMY10 and cosmid pDC100. Plasmid pMY 10 contained the origin of replication of pAL5000, the origin of replication of pBR322, a kanamycin resistance gene, and the origin of transfer of the Inc plasmid RK2; the cosmid pDC100 contained the pHC79 SS cosmid, the origin of replication of pAL5000, and a kanamycin resistance gene. The efficiency of transformation varied with the recipient cells used and was in decreasing order: 7×10⁵ forM. smegmatis MC²155, 6×10³ forM. tuberculosis H37Ra, 10³ forM. aurum, 50 forM. smegmatis ATCC 607, and 5 forM. flavescens. A rapid protocol for plasmid extraction from mycobacteria was developed.The satisfactory transformation of the nonvirulentM. tuberculosis strain H37Ra was of interest for future studies on cloning of virulence genes, while the satisfactory transformation ofM. aurum was of interest for future studies on the genetics of drug resistance because these bacteria are sensitive to drugs specifically used in the treatment of tuberculosis and leprosy. However, neither vector was stably maintained inM. smegmatis, indicating that further investigations are still necessary to resolve this difficulty.     

A new family of repetitive nucleotide sequences is restricted to the genus Zea

We have isolated a new family of moderately repetitive nucleotide sequences (about 2500 copies per haploid genome) specific to the genus Zea and absent in other graminaceous species. These sequences are interspersed in the genome and they show the same genomic organization pattern and similar copy number in all the Zea species examined. These two facts, consistency in the copy number and the same organization pattern, would indicate on the one hand that these sequences were amplified before the divergence of Zea species, and on the other hand that maize and all the teosintes could be considered as the same evolutionary population. Independent clones corresponding to the repetitive sequences have been isolated and sequenced from a genomic library of the teosinte, Zea diploperennis. The repeats, flanked by HaeIII sites, are more than 70% G + C-rich, on average 253 bp long and show 78% similarity to each other. These repetitive sequences are in a highly methylated-C context and they present some features resembling those of coding sequences, such as high CpG and low TpA content, and similar codon usage to maize genes in one of the reading frames. Moreover, the repetitive probe hybridizes with RNA extracted from different tissues of maize and from teosinte, indicating that these repeats or similar ones are present in transcribed sequences.     

Glandular trichomes and essential oil constituents ofCalamintha menthifolia (Lamiaceae)

Plant material ofCalamintha menthifolia was collected from two populations grown in the Vikos-Aoos area (NW. Greece). The structure and ontogeny of the glandular trichomes and the chemical composition of the secreted essential oil were studied. The leaves ofC. menthifolia have numerous glandular trichomes of three morphological distinct types: 1) glandular scales with a unicellular foot and stalk, and a 12-celled head, 2) glandular hairs with a unicellular foot and stalk, and a unicellular pear-shaped head and 3) glandular hairs with a unicellular foot, a bicellular stalk and a unicellular elongated head. Qualitative and quantitative GC-MS analyses of the essential oils revealed piperitone oxide as the main constituent in both populations. In the light of these results the relationships beweenC. menthifolia and other members of theSatureja group as well as its taxonomy are discussed.     

Ca2+ regulation of thyroid NADPH-dependent H2O2 generation

A thyroid particulate fraction contains an NADPH-dependent H2O2-generating enzyme which requires Ca2+ for activity. A Chaps solubilized extract of the thyroid particulate fraction partially purified by DEAE chromatography did not show a dependence on Ca2+ for activity. Preincubation of the particulate fraction with Ca2+ yielded a preparation insensitive to Ca2+. The non-particulate fraction obtained after incubation of the particles in the presence of Ca2+ was able to inhibit, in the presence of EGTA, the Ca2+-desensitized particulate fraction and the enzyme isolated on DEAE. It is concluded that the reversible Ca2+ activation of the NADPH-dependent H2O2 generation was modulated in porcine thyroid tissue by (a) calcium-releasable inhibitor protein(s).