Sequence variation in ZFX introns in human populations

DNA variation in human populations was studied by examining the last intron of the ZFX gene (about 1, 151 bp) with a worldwide sample of 29 individuals. Only one polymorphic site was found, which is located in an Alu sequence. This polymorphism is present at an intermediate frequency in all populations studied, and could be a shared polymorphism or due to migration among populations in Asia, Europe, and Africa. The nucleotide diversity is 0.04%, supporting the view that the level of nucleotide variation in nuclear DNA is very low in humans. From the sequence data, the age (T) of the most recent common ancestor of the sampled sequences is estimated: the mode of T is about 306,000 years, and the 95% confidence interval of T is 162,000-952,000 years. This mode estimate is considerably older than the estimates from Y- linked sequences.      

Primary cervical lymphoma: the role of cervical cytology

Two cases of primary malignant lymphoma of the uterine cervix are reported. Both were confirmed by histology as high grade B cell lymphomas. In one case, the diagnosis was made on a second colposcopic biopsy after an initial cervical smear and colposcopic biopsy were negative. In the second case, dyskaryotic cells of uncertain type were identified in a cervical smear taken at colposcopy performed as part of follow up for previous cervical intraepithelial neoplasia (CIN)I. The cytologic features and differential diagnosis of this rare cervical neoplasm are discussed, with emphasis on the role of the Papanicolaou smear in the initial diagnosis of this tumour.     

Re-establishment of the lady's slipper orchid (Cypripedium calceolus L.) in Britain

The Sainsbury Orchid Conservation Project (SOCP), based in the Micropropagation Unit of the Royal Botanic Gardens, Kew, has worked for many years with English Nature, and the Species Recovery Programme in particular, in raising plants of the lady's slipper orchid for re-establishment. This is a collaborative venture with the involvement of a large number of organizations and individuals at national and local level.Cypripedium calceolusis one of Britain's rarest plants. Thought at one time to be extinct, its decline is due to overcollection by botanists for herbarium specimens and by gardeners and it is found now on a single, fragile, natural site. It has been wardened since 1970s because of concerns about long-term safety and is protected under Schedule 8 of the Wildlife and Countryside Act 1981. Natural pollination has not been observed and hand pollination is carried out to ensure seed set. Some seed is scattered on site resulting in a few seedlings and the remaining capsules are sent to the Sainsbury Orchid Conservation Project. In addition, some plants of native origin are held in cultivation and molecular techniques are being carried out at Kew to ascertain how these are related. The best pollination strategy to increase genetic diversity is co-ordinated by English Nature and SOCP, as is the optimum collection time post-pollination to achieve maximum germination. Seedlings are propagated in the laboratory using immature green capsules sown on a range of nutrient media. No symbiotic fungus has yet been found for this species. Germination occurs after 6 weeks in the dark and the plants chilled when roots are well developed and shoots beginning to form. Plants potted up at Kew and near the native site have produced leaves and buds and extensive planting trials have now commenced. The main objective is to increase the number of localities whereCypripediumoccurs through re-establishment. As its decline is due to overcollection rather than habitat loss, many old sites have changed very little. Observation of continental populations is important in assessing suitability of potential sites as the extant clone may not be in optimum conditions. An initial planting trial on the wild site in winter 1989/90 resulted in a 75% survival rate of seedlings planted out. However, establishing seedlings is a long process and careful monitoring is required.     

Patterns of fungal diversity and composition along a salinity gradient

Estuarine salinity gradients are known to influence plant, bacterial and archaeal community structure. We sequenced 18S rRNA genes to investigate patterns in sediment fungal diversity (richness and evenness of taxa) and composition (taxonomic and phylogenetic) along an estuarine salinity gradient. We sampled three marshes—a salt, brackish and freshwater marsh—in Rhode Island. To compare the relative effect of the salinity gradient with that of plants, we sampled fungi in plots with Spartina patens and in plots from which plants were removed 2 years prior to sampling. The fungal sediment community was unique compared with previously sampled fungal communities; we detected more Ascomycota (78%), fewer Basidiomycota (6%) and more fungi from basal lineages (16%) (Chytridiomycota, Glomeromycota and four additional groups) than typically found in soil. Across marshes, fungal composition changed substantially, whereas fungal diversity differed only at the finest level of genetic resolution, and was highest in the intermediate, brackish marsh. In contrast, the presence of plants had a highly significant effect on fungal diversity at all levels of genetic resolution, but less of an effect on fungal composition. These results suggest that salinity (or other covarying parameters) selects for a distinctive fungal composition, and plants provide additional niches upon which taxa within these communities can specialize and coexist. Given the number of sequences from basal fungal lineages, the study also suggests that further sampling of estuarine sediments may help in understanding early fungal evolution.     

Can taxonomic distinctness assess anthropogenic impacts in inland waters? A case study from a Mediterranean river basin

1. It is increasingly recognised that adequate measures of biodiversity should include information on the ‘relatedness’ of species within ecological assemblages, or the phylogenetic levels at which diversity is expressed. Taxonomic distinctness measures provide a series of indices to achieve this, which are independent of sample size. Taxonomic distinctness has been employed widely in marine systems, where it has been suggested that this index can provide a reliable measure of anthropogenic impact. 2. We tested the behaviour of three related taxonomic distinctiveness indices (Average Taxonomic Distinctness, Δ⁺; Variation in Taxonomic Distinctness, Λ⁺; and Total Taxonomic Distinctness, sΔ⁺) in relation to putative levels of anthropogenic impact in inland waters and their potential utility in environmental monitoring, using an extensive data set for aquatic beetles from the south‐east of the Iberian Peninsula. 3. Taxonomic distinctness measures were not able to identify human disturbance effects and there were no clear relationships between these new biodiversity measures and the disturbance level recorded at individual localities. Furthermore, the taxonomic distinctness measures used were apparently less sensitive to the effects of anthropogenic impact than other diversity metrics, such as species richness and rarity. 4. We conclude that taxonomic distinctness indices may not always perform as well as other metrics in the assessment of environmental quality. In addition, taxonomic distinctness measure should be interpreted with caution, as their performance and ability to detect anthropogenic disturbance may depend on the phylogenetic structure of sampled taxa within a region, and their evolutionary and ecological history.     

Intronic gene conversion in the evolution of human X-linked color vision genes

Human red and green visual pigment genes are X-linked duplicate genes. To study their evolutionary history, introns 2 and 4 (1,987 and 1,552 bp, respectively) of human red and green pigment genes were sequenced. Surprisingly, we found that intron 4 sequences of these two genes are identical and that the intron 2 sequences differ by only 0.3%. The low divergences are unexpected because the duplication event producing the two genes is believed to have occurred before the separation of the human and Old World monkey (OWM) lineages. Indeed, the divergences in the two introns are significantly lower than both the synonymous divergence (3.2% +/- 1.1%) and the nonsynonymous divergence (2.0% +/- 0.5%) in the coding sequences (exons 1-6). A comparison of partial sequences of exons 4 and 5 of human and OWM red and green pigment genes supports the hypothesis that the gene duplication occurred before the human-OWM split. In conclusion, the high similarities in the two intron sequences might be due to very recent gene conversion, probably during evolution of the human lineage.      

Pulmonary segmental resection for solitary lesions of doubtful character

Pulmonary cancer can be diagnosed earlier if patients with pulmonary symptoms of chronic type are given x-ray examination early, if patients over 40 years of age have a yearly roentgen examination of the chest regardless of their state of health, and if those with acute pulmonary illness are examined by x-ray within one month of the onset of illness. Observation of a known intrapulmonary lesion of unknown character should never last for more than one month. If it persists after that period, complete investigation, including thoracotomy, should be carried out if necessary to establish an exact diagnosis. A localized intrapulmonary lesion can be removed by segmental resection so that all healthy functioning lung is conserved if the disease is benign. If, after pathological examination, the lesion is shown to be cancerous, more radical resection can be carried out.