European Lymnaeidae (Mollusca: Gastropoda), intermediate hosts of trematodiases, based on nuclear ribosomal DNA ITS-2 sequences.

Freshwater snails of the family Lymnaeidae are of a great parasitological importance because of the very numerous helminth species they transmit, mainly trematodiases of large medical and veterinary impact. The present knowledge on the genetics of lymnaeids and on their parasite-host inter-relationships is far from being sufficient. The family is immersed in a systematic-taxonomic confusion. The necessity for a tool which enables species distinction and population characterization is evident. This paper aims to review the European Lymnaeidae basing on the second internal transcribed spacer ITS-2 of the nuclear ribosomal DNA. The ITS-2 sequences of 66 populations of 13 European and 1 North American lymnaeid species, including the five generic (or subgeneric) taxa Lymnaea sensu stricto, Stagnicola, Omphiscola, Radix and Galba, have been obtained. The ITS-2 proves to be a useful marker for resolving supraspecific, specific and population relationships in Lymnaeidae. Three different groupings according to their ITS-2 length could be distinguished: Radix and Galba may be considered the oldest taxa (370-406 bp lengths), and Lymnaea s. str., European Stagnicola and Omphiscola (468-491 bp lengths) the most recent, American Stagnicola and Hinkleyia being intermediate (434-450 bp lengths). This hypothesis agrees with the phylogeny of lymnaeids based on palaeontological data, chromosome numbers and radular dentition. ITS-2 sequences present a conserved central region flanked by two variable lateral regions corresponding to the 5' and 3' ends. The number of repeats of two microsatellites found in this conserved central region allows to differentiate Radix from all other lymnaeids. Phylogenetic trees showed four clades: (A) Lymnaea s. str., European Stagnicola and Omphiscola; (B) Radix species; (C) Galba truncatula; and (D) North American stagnicolines. ITS-2 results suggest that retaining Stagnicola as a subgenus of Lymnaea may be the most appropriate and that genus status for Omphiscola is justified. Radix shows a complexity suggesting different evolutionary lines, whereas G. truncatula appears to be very homogeneous. North American and European stagnicolines do not belong to the same supraspecific taxon; the genus Hinkleyia may be used for the American stagnicolines. Genetic distances and sequence differences allowed us to distinguish the upper limit to be expected within a single species and to how different sister species may be. S. palustris, S. fuscus and S. corvus proved to be valid species, but S. turricula may not be considered a species independent from S. palustris. Marked nucleotide divergences and genetic distances detected between different S. fuscus populations may be interpreted as a process of geographic differentiation developping in the present. Among Radix, six valid species could be distinguished: R. auricularia, R. ampla, R. peregra (=R. ovata;=R. balthica), R. labiata, R. lagotis and Radix sp. The information which the ITS-2 marker furnishes is of applied interest concerning the molluscan host specificity of the different trematode species. The phylogenetic trees inferred from the ITS-2 sequences are able to differentiate between lymnaeids transmitting and those non-transmitting fasciolids, as well as between those transmitting F. hepatica and those transmitting F. gigantica. The Fasciola specificity is linked to the two oldest genera which moreover cluster together in the phylogenetic trees, suggesting an origin of the Fasciola ancestors related to the origin of this branch. European Trichobilharzia species causing human dermatitis are transmitted only by lymnaeids of the Radix and Lymnaea s. str.-Stagnicola groups. Results suggest the convenience of reinvestigating compatibility differences after accurate lymnaeid species classification by ITS-2 sequencing. Similarly, ITS-2 sequencing would allow a step forward in the appropriate rearrangement of the actual systematic confusion among echinostomatids.     

Influence of age and duration of symptoms on fibre type distribution and size of the back muscles in chronic low back pain patients

Many studies have documented an association between chronic low back pain (LBP) and deficits in back muscle strength and endurance. The sub-optimal performance is believed to be the result of alterations in the size and structure of the muscle, although the long-standing issue of whether the observed changes precede or are a consequence of the pain remains unresolved. If consequent to the problem, and predominantly related to disuse of the muscles, then it may be expected that a relationship between muscle structure and symptom duration would exist. Lumbar paraspinal muscle samples were obtained from 59 chronic LBP patients using the percutaneous biopsy technique. The samples were subject to routine histochemical analysis for the examination of muscle fibre type characteristics and cytochemical architectural changes. In 55 of the patients, the gross cross-sectional areas of magnetic resonance images of the trunk muscles were also measured. Multivariate analysis showed that symptom duration was the strongest predictor of the individual proportions of the fast-fatigable type IIX fibres; with age and gender included in the model, nearly 30% of the variance in fibre type distribution could be accounted for. Duration of pain had no influence on fibre size. Gross muscle cross-sectional area correlated directly with lean body mass and inversely with age, but showed no relationship with symptom duration. Pathological changes in the internal fibre structure were more frequently encountered in older patients, and were independent of symptom duration. The results suggest that, over the long term, fibre type transformations rather than alterations in fibre size are the predominant changes to be found in the muscles of chronic LBP patients. The direction of change supports the results of many previous studies that have demonstrated corresponding differences in the fatigability of the muscles. There is a strong case for the early implementation of active measures to attempt to offset the development of these changes in back pain patients. Received: 9 June 2000 / Accepted: 20 June 2000     

The emerging dental workforce: long-term career expectations and influences. A quantitative study of final year dental students' views on their long-term career from one London Dental School

Background  

Research into the motivation and expectations of the emerging workforce and their short-term expectations has already been reported with a view to informing professional and policy decisions. The objective of this component of the research programme was to examine the long-term goals and perceived influences on final year dental students' professional careers.     

Recurrent involvement of 2p23 in inflammatory myofibroblastic tumors.

Inflammatory myofibroblastic tumor (IMT) is a relatively rare soft tissue tumor. The reactive versus neoplastic pathogenesis of this tumor is unresolved. We found clonal chromosome aberrations involving 2p23 upon metaphase analysis of two IMTs. Fluorescence in situ hybridization with a probe flanking the ALK gene at 2p23 demonstrated rearrangement of the probe in both of these cases and in a third case, and immunohistochemistry revealed ALK expression in all three cases. 2p22-24 involvement has been reported previously in four additional cases of IMT. We suggest that chromosomal rearrangements involving 2p23 near or within ALK are recurrent alterations in IMT and that ALK may have a novel role outside its previously recognized realm of lymphoid neoplasms.     

Development of human mast cells in vitro.

Nucleated cells of human umbilical cord blood were cocultured with mouse skin-derived 3T3 fibroblasts. After 7-8 weeks in culture, when the number of the other hematopoietic cells declined, metachromatic granule-containing mononuclear cells appeared in the cultures, and the number of the cells increased up to 12 weeks. After 11-14 weeks in culture, the metachromatic mononuclear cells comprised a substantial portion of the cultured cells. These cells contained 1.8-2 micrograms of histamine per 10(6) cells and bore receptors for IgE. All of the cells contained tryptase in their granules. Electron microscopic analysis showed that these cells were mature human mast cells, clearly different from the basophilic granulocytes or eosinophils that arise in a variety of circumstances in cord blood cell cultures. Most of the cultured mast cells expressed some granules with regular crystalline arrays and contained both tryptase and chymase, and thus resembled human skin mast cells.     

Factors related to accuracy in office cholesterol testing. Iowa Academy of Family Physicians Research Network

BACKGROUND. There has been growing interest in the performance of diagnostic testing in physician office laboratories (POLs). Since the measurement of cholesterol is a well-defined and standardized laboratory test, it was selected to assess factors related to test accuracy in POLs. METHODS. One hundred thirty-one family practice offices were eligible to participate in the survey. Each was mailed a cholesterol specimen with a standardized value in October 1988. The laboratory characteristics of those POLs with results that were within 10% of the true specimen value were compared with those with results that were greater than 10% in error. RESULTS. Of the 131 POLs, 122 returned an answer for the unknown specimen. Ninety-eight (80%) were within 10% of the true value, and 114 (93%) were within 15%. Factors that were related to lower error rates (more likely to be within 10% total error) were whether the laboratory performed more than 25 laboratory tests per day, participated in a proficiency testing program, and ran daily quality controls, as well as the type of instrument the laboratory used. CONCLUSIONS. Overall performance of the POLs compared favorably with reference laboratories; however, running controls and participating in a proficiency testing program may further improve POL test accuracy.