Survey of human and rat microsatellites

Length variations in simple sequence tandem repeats (microsatellite DNA polymorphisms) are finding increasing usage in mammalian genetics. Although every variety of short tandem repeat that has been tested has been shown to exhibit length polymorphisms, little information on the relative abundance of the different repeat motifs has been collected. In this report, summaries of GenBank searches for all possible human and rat microsatellites ranging from mononucleotide to tetranucleotide repeats are presented. In humans, the five most abundant microsatellites with total lengths for the runs of repeats of greater than or equal to 20 nucleotides contained repeat sequences of A, AC, AAAN, AAN, and AG, in order of decreasing abundance, where N is C, G, or T. These five groups comprised about 76% of all microsatellites. Many other human simple sequence repeats were found at low frequency. In the 745 kb of human genomic DNA surveyed, one microsatellite of greater than or equal to 20 nucleotides in length was found, on average, every 6 kb. Only 12% of the human microsatellites had total lengths greater than or equal to 40 nucleotides. Roughly 80% of the A, AAN, and AAAN microsatellites and 50% of the AT microsatellites, but few of the other human microsatellites, were found to be associated with interspersed, repetitive Alu elements. In rats, the five most abundant microsatellites contained AC, AG, A, AAAN, and AAGG sequences, respectively. Rat microsatellites were generally longer than human microsatellites, with 43% of the rat sequences greater than or equal to 40 nucleotides.     

Novel DNA structures resulting from dTam3 excision in tobacco

A Tam3 two-element system has been designed by combining an immobilized Tam3 element with a non-autonomous dTam3 element inserted into the HPT gene. The phenotypic assay employed, restored hygromycin resistance, indicated thattrans-activation of the non-autonomous dTam3 element occurred. Molecular analyses of the excision sites revealed that the ends of the dTam3 element remain in the empty donor sites. The predominant consequence of this type of excision appears to be that excised fragments fail to re-integrate into the tobacco genome. Only one case of dTam3 re-integration could be detected. The ends of this element had been degraded upon integration into the tobacco genome. Either the altered structure of the Tam3 derivatives or tobacco host factors are influencing thetrans-activation of a dTam3 element, resulting in aberrant excision.     

Seabirds and marine mammals in the eastern Barents Sea: late summer at-sea distribution and calculated food intake

The at-sea distribution of seabirds and marine mammals in the eastern Barents Sea was determined using standardized transect counts during three cruises of RV“Dalnie Zelentsy” (Murmansk) in late summer 1991, 1992 and 1993. Totals of 32,268 seabirds, 485 pinnipeds, 25 cetaceans and 4 polar bears were counted during 554 half-hour counts. Numbers were converted into densities, total biomass and calculated daily food intake. Mean total food intake in kg fresh weight/km².day was 3.1 for the entire zone and all years; fish eaters dominated the whole region, with an intake of 1.3 (mainly Brünnich’s guillemot, Uria lomvia, and harp seal, Phoca groenlandica), followed by zooplankton eaters (0.85, mainly fulmar, Fulmarus glacialis) and mixed zooplankton and fish feeders (0.75, mainly minke whale, Balaenoptera acutorostrata, and kittiwake, Rissa tridactyla). Year-to-year variations were of little importance, while geographic differences were obvious between Norwegian coastal, Atlantic and Barents Sea water masses, both quantitatively and qualitatively (relative importance of main diets). Within each zone, a strong geographic heterogeneity was noted, with high local concentrations at fronts between water masses and at ice edges.     

Physical properties of methylcelluloses in relation with the conditions for cellulose modification

A high molecular weight glycoprotein antigen was isolated by size exclusion chromatography on Sepharose 4B from an extract of the yeast Saccharomyces cerevisiae. The glycoprotein antigen Sc 500 was shown to be identical to the antigen termed gp200 previously isolated (Heelan et al., 1991). The MW of Se 500 was determined to be about 500 kDa by size exclusion chromatography on Superose 6 and 460 kDa ± 20k Da by size-exclusion chromatography/multi-angle laser light scattering (SEC/MALLS). Sc 500 contained 90% mannose and traces of N-acetylglucosamine. The amino acid composition revealed that serine and threonine were the most abundant amino acids of the protein part. By alkaline borohydride treatment some, but not all bonds between protein and carbohydrate were broken. This indicates that the main type of linkage between protein and carbohydrate is O-glycosidic and that a minor type is of N-glycosidic nature. Methylation analysis revealed that the mannose residues were connected by 1 → 2 and 1 → 3 linkages with 1 → 2, 1→ 6 linked branch points.

Purified Sc 500 was subjected to a series of chemical and enzymatic modifications followed by studies of antibody binding activity. Treatments with both periodate and alkaline sodium borohydride reduced the human serum IgA, IgG and monoclonal IgM antibody binding activity of Sc 500 whereas trypsin and pronase did not affect its ability to bind these antibodies. The mannosidase Man1 → 2,3,6Man reduced the IgM binding to Sc 500 while the other enzymes included in this experiment (Man1→2 Man, Manβ1 →4GlcNAc and PNGase F) had no effect on the antibody binding.     

Peroxisome proliferators as inducers and substrates of UDP-glucuronosyltransferases

Summary— Peroxisome proliferators, despite their chemically unrelated structures, share the common property of being able to stimulate the glucuronidation of bilirubin in rodents and, probably, also in man. The aryloxycarboxylic acids (clofibric acid, fenofibrate, bezafibrate, ciprofibrate), tiadenol and probucol, all of which have hypolipidemic properties, as well as the fatty acid-like perfluorodecanoic acid all enhanced the expression of the UDP-glucuronosyltransferase (UGT) form involved in the conjugation of the pigment. This induction is manifested by an increase in the mRNA species encoding the protein with a subsequent increase in the neosynthesis of the corresponding protein in the endoplasmic reticulum. The induction process is concomitant with that of cytochrome P-450-IVA1 and cytosolic epoxide hydrolase, which, like bilirubin UGT, are mainly involved in the metabolism of endogenous substrates. With a series of carboxylic acids related to clofibric acid, it was possible to demonstrate that induction was mediated via specific interactions based on the physicochemical properties of the inducers. Until now, the molecular basis of induction of bilirubin UGT is not known. The peroxisome proliferators that possess a carboxyl group are good substrates of UGT, especially in man. The acylglucuronides formed are known for their instability and reactivity which could contribute to the toxicity encountered in some patients treated with the drugs. There is convincing evidence that UGT bilirubin does not catalyze the glucuronidation of these substances even if the two types of substrate form acylglucuronides.     

Analysis of human V H gene repertoire expression in peripheral CD19+ B cells

Using CD19 B-cell selection and polymerase chain reaction-amplified cDNA libraries, we analyzed the peripheral immunoglobulin heavy chain variable repertoire of three healthy adult donors. Here we report that most of the CD19+ circulating B cells expressed unmutated V _H-D-J_H rearrangements. By specific V _H family hybridization, we show that V _H gene family utilization in the periphery roughly corresponds to the complexity of these families in the germline and appears to be relatively constant among the analyzed subjects. However, sequence data of clones picked at random from one IgM cDNA library reveals that in spite of this random utilization, the V _H gene expression in naive circulating B cells is highly biased towards the expression of a limited set of V _H genes. As previously reported by others, this restricted mechanism is also found for the D and J _H segments.The nucleotide sequence data reported in this paper have been submitted to the GenBank/EMBL nucleotide sequence database and have been assigned the accession numbers Z47213-Z47243 and Z47349     

Isolation of methotrexate-resistant cell lines in Petunia hybrida upon stepwise selection procedure

Summary Cell suspensions of Petunia hybrida were subjected to a selection procedure in which the concentration of the selective agent, methotrexate (MTX), was gradually elevated. In mammalian cells, this procedure frequently results in MTX-resistant mutants due to amplification of the gene coding for dihydrofolate reductase (DHFR), the target protein of MTX.Five suspension lines were isolated, with degrees of resistance ranging from 10 to 500 M MTX (in wild type the LD_99.9 is 0.2 M). MTX^R phenotypes were unstable, as manifested by the loss of resistance upon prolonged growth in the absence of drug. All of the mutants also exhibited high values of MTX-binding protein (60- to 400-fold higher than that of the wild type), which declined to intermediate values upon MTX withdrawal. Finally, cellular extracts from all of the mutants also showed high specific staining of DHFR-activity in gels.The results suggest that the resistance of MTX in these plant cell-lines is mediated by the elevation of the amounts of DHFR, probably as a consequence of gene amplification.     

Microspatial heterogeneity in the distribution of ciliates in a small pond

Five transects of contiguous samples from the surface of a small pond and one transect from its bottom were collected in order to quantify microspatial heterogeneity in the distribution of ciliated protozoa. Examination of the frequency-abundance relations for these transects suggests that they can be approximated by negative binomial distributions with a commonk of 1.87. Contagiousness or crowding increases with population density.Mean patch size and mean interpatch distance were measured for 4 transects as 1.5 to 2 cm and 3 to 4 cm, respectively. This heterogeneity is suggested to arise from behavioral aggregation about discrete food sources and be very ephemeral.Blocking of adjacent contiguous samples was used to investigate the effect of sample size on the apparent correlation between the numbers of pairs of taxa. In all cases examined, taxa were relatively independent in their distribution at small sample sizes and became more negatively or positively associated as samples were combined. This may reflect that the small scale patches are essentially monospecific.     

Contribution to the structural characterization of eucaryotic PSI reaction centre—I. Critical analysis of the polypeptidic composition of different P700 enriched fractions

In thylakoid membranes, several peptides of high MW are present which may interfere with the study of CP1's components. Modifying Cleveland's technique [7] for limited proteolysis, we have characterized the polypeptides found in the 60 kD region. Some may result from incomplete washing of the CF1 while others come from the CP1; indeed, this chlorophyll protein complex, which has a higher MW (above 100 kD), very often undergoes a dissociation into smaller components of about 60 KD MW.Analysis of the protein content of different preparations commonly used to obtain PSI reaction centre enriched fractions has been performed. The and subunits of CF1 are among the main contaminants of most of these preparations. A further purification step is described which can be applied to all these preparations, but numerous peptides are still present in the active fractions. It is most unlikely that all these polypeptides are required for the primary photochemical event, and this emphasizes the necessity to find a new simple method to purify PSI reaction centres.