Sequence variations in small-subunit ribosomal RNAs of Hartmannella vermiformis and their phylogenetic implications

Evidence of associations between free-living amoebas and human disease has been increasing in recent years. Knowledge about phylogenetic relationships that may be important for the understanding of pathogenicity in the genera involved is very limited at present. Consequently, we have begun to study these relationships and report here on the phylogeny of Hartmannella vermiformis, a free-living amoeba that can harbor the etiologic agent of Legionnaires' disease. Our analysis is based on studies of small-subunit ribosomal RNA genes (srDNA). Nucleotide sequences were determined for nuclear srDNA from three strains of H. vermiformis isolated from the United Kingdom, Germany, and the United States. These sequences then were compared with a sequence previously obtained for a North American isolate by J. H. Gunderson and M. L. Sogin. The four genes are 1,840 bp long, with an average GC content of 49.6%. Sequence differences among the strains range are 0.38%-0.76%. Variation occurs at 19 positions and includes 2 single-base indels plus 14 monotypic and 3 ditypic single-base substitutions. Variation is limited to eight helix/loop structures according to a current model for srRNA secondary structure. Parsimony, distance, and bootstrap analyses used to examine phylogenetic relationships between the srDNA sequences of H. vermiformis and other eukaryotes indicated that Hartmannella sequences were most closely related to those of Acanthamoeba and the alga Cryptomonas. All ditypic sites were consistent with a separation between European and North American strains of Hartmannella, but results of other tests of this relationship were statistically inconclusive.      

Endothelin receptor B polymorphism associated with lethal white foal syndrome in horses

Overo lethal white syndrome (OLWS) is an inherited syndrome of foals born to American Paint Horse parents of the overo coat-pattern lineage. Affected foals are totally or almost totally white and die within days from complications due to intestinal aganglionosis. Related conditions occur in humans and rodents in which mutations in the endothelin receptor B (EDNRB) gene are responsible. EDNRB is known to be involved in the developmental regulation of neural crest cells that become enteric ganglia and melanocytes. In this report we identify a polymorphism in the equine EDNRB gene closely associated with OLWS. This Ile to Lys substitution at codon 118 is located within the first transmembrane domain of this seven-transmembrane domain G-protein-coupled receptor protein. All 22 OLWS-affected foals examined were homozygous for the Lys118 EDNRB allele, while all available parents of affected foals were heterozygous. All but one of the parents also had an overo white body-spot phenotype. Solid-colored control horses of other breeds were homozygous for the Ile118 EDNRB allele. Molecular definition of the basis for OLWS in Paint Horses provides a genetic test for the presence of the Lys118 EDNRB allele and adds to our understanding of the basis for coat color patterns in the horse. Received: 13 September 1997 / Accepted: 2 December 1997     

The Epidemiology of Dental Diseases in the Elderly1

This paper summarizes and evaluates epidemiologic evidence on adult dental conditions with a focus on older adults. Information is presented on coronal caries; root caries; loss of teeth, attrition, abrasion, and erosion; periodontal diseases; and oral cancer. The author concludes that the oral health status of the elderly in the United States is essentially unknown. There are no recent, representative population base studies of oral conditions in the elderly. Studies of prevalence or incidence of oral diseases typically include few elderly persons or describe a select group of elderly who are at high risk. Furthermore, it is not really known whether the incidence and prevalence of coronal caries or root caries is actually increasing or is part of a cohort effect. While oral cancers have been shown to increase with age, there is no information as to whether their incidence rates are increasing. While, clinically, there are indications that attrition, abrasion and erosion are characteristics that are more likely to be seen in older adults, there is no information about their distribution in the population. There is evidence that loss of teeth is decreasing but nothing is known about the patterning of that loss. As for periodontal diseases, much work is needed to identify various syndromes that may be distinguished by their distribution in the population as well as determining whether periodontitis is a condition responsible for a majority of tooth loss or just the majority of tooth loss in a small high risk group. In addition, some suggestions are presented for future directions of research in this area.     

Pitfalls in Portacath location using the landmark technique: case report

A 34 year old woman diagnosed with breast cancer and liver metastases underwent a left subclavian Portacath insertion. During the procedure, the clinical features and the findings of intra-operative investigations provided conflicting evidence of the catheter position. This report highlights the potential difficulties in establishing long-term central venous access, the limitations of common investigations and safety issues relating to the process of subclavian line insertion.