In vivo selection of lymphocyte-tropic and macrophage-tropic variants of lymphocytic choriomeningitis virus during persistent infection.

This study demonstrates cell-specific selection of viral variants during persistent lymphocytic choriomeningitis virus infection in its natural host. We have analyzed viral isolates obtained from CD4+ T cells and macrophages of congenitally infected carrier mice and found that three types of variants are present in individual carrier mice: (i) macrophage-tropic, (ii) lymphotropic, and (iii) amphotropic. The majority of the isolates were amphotropic and exhibited enhanced growth in both lymphocytes and macrophages. However, some of the lymphocyte-derived isolates grew well in lymphocytes but poorly in macrophages, and a macrophage-derived isolate replicated well in macrophages but not in lymphocytes. In striking contrast, the original wild-type (wt) Armstrong strain of lymphocytic choriomeningitis virus that was used to initiate the chronic infection and from which the variants are derived grew poorly in both lymphocytes and macrophages. These three types of variants also differed from the parental virus in their ability to establish a chronic infection in immunocompetent hosts. Adult mice infected with the wt Armstrong strain cleared the infection within 2 weeks, whereas adult mice infected with the variants harbored virus for several months. These results suggest that the ability of the variants to persist in adult mice is due to enhanced replication in macrophages and/or lymphocytes. This conclusion is further strengthened by the finding that the variants and the parental wt virus grew equally well in mouse fibroblasts and that the observed growth differences were specific for cells of the immune system.     

A genetic code alteration generates a proteome of high diversity in the human pathogen <Emphasis Type="Italic">Candida albicans</Emphasis>

Background  

Genetic code alterations have been reported in mitochondrial, prokaryotic, and eukaryotic cytoplasmic translation systems, but their evolution and how organisms cope and survive such dramatic genetic events are not understood.     

Genetic variability in the complete mitochondrial control region of the Eurasian otter (Lutra lutra) in the Iberian Peninsula

Sequencing of the complete mitochondrial DNA control region from 31 samples of the Eurasian otter, Lutra lutra , enabled us to establish the length and structure of this fragment, as well as to describe, for the first time, the RS3 repetitive region located at the 3' end. In addition, genetic variability of the 5' end was examined in 63 individuals, 57 of which were wild otters from the Iberian Peninsula and six captive reared otters. This analysis resulted in extremely low variability. All the samples from the Iberian Peninsula share a single haplotype, Lut 1, the most common haplotype in Europe. Captive otters showed two haplotypes: Lut 3, which has been described in wild otters from eastern Germany, and Lut 6, an haplotype not described to date. Higher variability was observed in the repetitive RS3 region. The tandem repeat was composed of an array of ten repeat units of 22 bp with differences in the repetitive motifs that differed in the arrays of different specimens. In total, 20 different haplotypes from 31 individuals were found. However, the geographical distribution of these haplotypes did not generate a phylogeographical signal. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 86 , 397–403.     

Purification of amyloglucosidase

Amyloglucosidase (glucoamylase; EC 3.2.1.3) has been purified from the culture filtrates of Aspergillus candidus Link var. aureus using hydrophobic interaction chromatography and DEAE-cellulose treatment. The enzyme thus obtained has a specific activity of 329 units/mg protein with the overall recoveries between 70 and 75%. The process appears to be of industrial promise.     

Phosphorus supply drives rapid turnover of membrane phospholipids in the diatom Thalassiosira pseudonana

In low-phosphorus (P) marine systems, phytoplankton replace membrane phospholipids with non-phosphorus lipids, but it is not known how rapidly this substitution occurs. Here, when cells of the model diatom Thalassiosira pseudonana were transferred from P-replete medium to P-free medium, the phospholipid content of the cells rapidly declined within 48 h from 45±0.9 to 21±4.5% of the total membrane lipids; the difference was made up by non-phosphorus lipids. Conversely, when P-limited T. pseudonana were resupplied with P, cells reduced the percentage of their total membrane lipids contributed by a non-phosphorus lipid from 43±1.5 to 7.3±0.9% within 24 h, whereas the contribution by phospholipids rose from 2.2±0.1 to 44±3%. This dynamic phospholipid reservoir contained sufficient P to synthesize multiple haploid genomes, suggesting that phospholipid turnover could be an important P source for cells. Field observations of phytoplankton lipid content may thus reflect short-term changes in P supply and cellular physiology, rather than simply long-term adjustment to the environment.     

A high level interface to SCOP and ASTRAL implemented in Python

Background  

Benchmarking algorithms in structural bioinformatics often involves the construction of datasets of proteins with given sequence and structural properties. The SCOP database is a manually curated structural classification which groups together proteins on the basis of structural similarity. The ASTRAL compendium provides non redundant subsets of SCOP domains on the basis of sequence similarity such that no two domains in a given subset share more than a defined degree of sequence similarity. Taken together these two resources provide a 'ground truth' for assessing structural bioinformatics algorithms. We present a small and easy to use API written in python to enable construction of datasets from these resources.     

莱茵衣藻Nfr-4突变株中类胡萝卜素含量的变化及其对藻生长的影响

文章对相同条件下培养的莱茵衣藻野生型CC-137和八氢番茄红素脱氢酶(phytoene desaturase,PDS)基因突变株Nfr-4的生长进行分析;并用反相高效液相色谱分析总有色类胡萝卜素以及叶绿素含量变化,结果表明两者生长的差异明显;Nfr-4突变株的单细胞叶绿素和总有色类胡萝卜素含量高于野生型CC-137的。     

Karyological studies in Sonchus section Muritimi (Asteraceae) from the Iberian Peninsula

MEJÍAS, J. A. & VALDÉS, B., 1988. Karyologiepl studies in Sonchus section Madtimi (Asteraceae) from the Iberian Peninmula. Karyological data support the distinction of S. aquatilis Pourret and S. maritimus L. at the specific level. Karyological data and hybridization experiments support the idea that S. × novocaslcllanus Cirujano has been produced by the hybridization of S. crassifolius Pourret ex Willd. and S. maritimus L.