Presence and Analysis of Plasmids in Human and Animal Associated Arcobacter Species

In this study, we report the screening of four Arcobacter species for the presence of small and large plasmids. Plasmids were present in 9.9% of the 273 examined strains. One Arcobacter cryaerophilus and four Arcobacter butzleri plasmids were selected for further sequencing. The size of three small plasmids isolated from A. butzleri and the one from A. cryaerophilus strains ranged between 4.8 and 5.1 kb, and the size of the large plasmid, isolated from A. butzleri, was 27.4 kbp. The G+C content of all plasmids ranged between 25.4% and 26.2%. A total of 95% of the large plasmid sequence represents coding information, which contrasts to the 20 to 30% for the small plasmids. Some of the open reading frames showed a high homology to putative conserved domains found in other related organisms, such as replication, mobilization and genes involved in type IV secretion system. The large plasmid carried 35 coding sequences, including seven genes in a contiguous region of 11.6 kbp that encodes an orthologous type IV secretion system found in the Wolinella succinogenes genome, Helicobacter pylori and Campylobacter jejuni plasmids, which makes this plasmid interesting for further exploration.     

Book Reviews

Book reviewed in this article:
Applied Anthropology: The Aboriginal Arts and Crafts Industry . Jon Altman
Marketing Aboriginal Art in the 1990s . Jon Altman and Luke Taylor     

Age-related changes in oxidized proteins

We have previously described the oxidative inactivation of several key metabolic enzymes by a variety of mixed function oxidation systems. Because many of the enzymes which are inactivated have been shown by others to accumulate as inactive or less active forms during cellular aging, we have examined the levels of oxidatively modified proteins in two model systems used for studies on aging. The results show that levels of oxidatively modified proteins increase with age in circulating erythrocytes, and this change is correlated with the loss of marker enzyme activity. Our studies also show that in cultured fibroblasts from normal donors the levels of oxidatively modified proteins increase only after the age of 60. However, the levels of oxidatively modified proteins in fibroblasts from individuals with progeria or Werner's syndrome are significantly higher than age-matched controls. Moreover, treatment of glucose-6-phosphate dehydrogenase with a mixed function oxidation system leads to oxidative modification and increased heat lability of the enzyme. Taken together these results suggest that loss of functional enzyme activity and increased heat lability of enzymes during aging may be due in part to oxidative modification by mixed function oxidation systems.     

Dynamics of long-leaved sundew Drosera intermedia populations at two extremes of a hydrological gradient

Densities of Drosera intermedia were low in two studied habitats (10–25 ramets m⁻¹), a path through a wet heath (short inundation in spring, low soil moisture in summer) and a pool edge (longlasting inundation, high soil moisture in summer). The low densities could be explained by the observed low recruitment and high adult mortality.
The low recruitment resulted from: (1) a high first year mortality of the large number of seedlings that emerged each year in the path population, caused by summer drought and cover with algae after heavy rainfall; (2) the absence in two years out of three of seedling emergence at the pool edge, due to the longlasting inundation. In neither population any seedlings survived to flower; (3) low vegetative reproduction rate.
Adult mortality during the growing season was caused by drought, which did not occur at the pool edge. Rapid senescence in autumn, caused by summer drought on the path and by a rapid submersion after heavy rainfall at the pool edge, was associated with a high winter mortality.     

The reproductive behaviour of a clonal herbaceous plant, the longleaved sundew Drosera intermedia, in different heathland habitats

The reproductive behaviour of the longleaved sundew Drosera intermedia Hayne was studied in three hydrologically differing heathland habitats a pool edge, an old path through the wet heath and a seepage area
Sexual reproductive allocation (SRA) (the slope of the regression of sexual biomass on vegetative biomass m a given season) differed strongly between years (related to temperature and precipitation) and habitats Averaged over years, path plants had a higher SRA than plants in the seepage area and at the pool edge
Asexual reproductive allocation, expressed as the size-dependent probability of reproducing asexually, did not differ between habitats in most years
The observations agreed with general life history theory SRA was high in the path habitat where adult survival chances were low and juvenile (= seed, first year seedling) survival was high SRA was lower in the seepage area where adult survival chances were higher and juvenile survival lower At the pool edge, a habitat with high adult mortality and low juvenile establishment, the predicted optimal reproductive behaviour, a high SRA, was not observed due to environmental constraints (inundation)     

Germline excision of the transposable element Tc1 in C. elegans.

We have examined eight germline revertants generated by the excision of Tc1 from a site within the unc-22 gene of Caenorhabditis elegans. A rich variety of rearrangements accompanied Tc1 excision at this site, including transposon 'footprints', deletions of sequences flanking the insertion site and direct nontandem duplications of flanking DNA. With only modest modification the double-strand gap repair model for transposition, recently proposed by Engles and coworkers (Cell 62: 515-525 1990), can explain even the most complex of these rearrangements. In light of this model rearrangements of the target site accompanying transposition/excision may not be the end result of imprecise excision of the element. Instead, these rearrangements may be the result of imprecise repair of the double-strand gap by the host replication and repair machinery. Sequences surrounding an insertion site influence the fidelity of gap repair by this machinery. This may lead to a number of possible resolutions of a double-strand gap as documented here for a Tc1 site in unc-22.     

Polycystic renal diseases: morphology and genetic counseling

The designation "polycystic kidneys" is vague and causes considerable confusion. This term comprises a number of affections, characterized by the presence of renal cysts. Cystic kidneys may be hereditary or sporadic. The defect may be isolated or occur as part of a syndrome. The identification of the exact nature of the lesion is therefore of paramount importance, not only for the prognosis of the propositus, but especially for the correct genetic counselling of the family. In this context, the perinatal autopsy represents an irreplaceable method of investigation. Since the pathogenesis of many, if not all, types of polycystic kidneys remains unknown, a practical classification must be based on gross and microscopic pathologic study, clinical features, and family history. Osathanondh and Potter (1964) distinguished four varieties, based on morphological findings, revealed by microdissection. Unfortunately, not all types of cystic kidneys are included in this classification. Moreover, their type III cystic kidney collects a number of clearly different entities. Nevertheless, once one is familiar with its deficiencies, the Osathanondh and Potter classification is still very useful.