FUNGAL SYMBIONTS. Global assessment of arbuscular mycorrhizal fungus diversity reveals very low endemism.

The global biogeography of microorganisms remains largely unknown, in contrast to the well-studied diversity patterns of macroorganisms. We used arbuscular mycorrhizal (AM) fungus DNA from 1014 plant-root samples collected worldwide to determine the global distribution of these plant symbionts. We found that AM fungal communities reflected local environmental conditions and the spatial distance between sites. However, despite AM fungi apparently possessing limited dispersal ability, we found 93% of taxa on multiple continents and 34% on all six continents surveyed. This contrasts with the high spatial turnover of other fungal taxa and with the endemism displayed by plants at the global scale. We suggest that the biogeography of AM fungi is driven by unexpectedly efficient dispersal, probably via both abiotic and biotic vectors, including humans.

The effect of a diuretic (hydrochlorothiazide) on tear production in humans.

The effect of an orally administered diuretic, hydrochlorothiazide, on tear production in 11 normal young human subjects (five men and six women, 18 to 35 years old) was measured in a single-masked study. Schirmer tests with topical anesthetic showed a significant (P = .02) decrease in basal aqueous tear production on days when these subjects were taking the diuretic. The average decrease was 2.1 mm of wetting in five minutes.

Outcomes of cleft care in Western Australia: a pilot study.

The purpose of this study was to compare outcomes and delivery of cleft care in Western Australia with the average standard of care in the United Kingdom (UK). This was achieved through a cross-sectional study involving children born with unilateral cleft lip and palate between April 1983 and March 1985 (12 year olds) or between April 1990 and March 1992 (5 year olds). A total of 38 children born with unilateral cleft lip and palate were under the care of the cleft team based at Perth's Princess Margaret Hospital. Dental arch relations, facial skeletal pattern, speech, hearing, success of alveolar bone grafting and dental health were measured. It was found that fewer Princess Margaret Hospital children in both age cohorts had revision surgery and speech therapy compared with the UK average. The facial skeletal pattern, speech, hearing and alveolar bone grafting outcomes from Princess Margaret Hospital were similar to the UK at age 12. Seventeen per cent of the Princess Margaret Hospital 12 year olds had a poor dental arch relationship compared with 39 per cent in the UK. In the 5 year olds, most outcomes in Princess Margaret Hospital patients appeared better than the UK with lower residual treatment needs. While it is difficult to draw firm conclusions because of the small numbers involved, this study indicates standards need to be set and determined for Australia.

Tooth position and speech--is there a relationship?

Although it is widely accepted that teeth play an important role in speech production, the relationship between tooth position and speech remains controversial. This review paper examines the relevant studies and discusses the difficulties of scientific investigation in this area. The ability of patients to adapt their speech to compensate for abnormal tooth position is recognized, but the mechanisms for this adaptation remain incompletely understood. The overall conclusion is that while certain dental irregularities show a relationship with speech disorders, this does not appear to correlate with the severity of the malocclusion. There is no definitive proof that alteration of tooth position can improve articulation disorders.

XG: the forgotten blood group system.

The XG blood group system is best known for its contributions to the fields of genetics and chromosome mapping. This system comprises two antigens, Xg(a) and CD99, that are not antithetical but that demonstrate a unique phenotypic relationship. XG is located on the tip of the short arm of the X chromosome with exons 1 to 3 present in the pseudoautosomal region of the X (and Y) chromosome(s) and exons 4 to 10 located only on the X chromosome. Xg(a) demonstrates a clear X-linked pattern of inheritance. MIC2, the gene encoding the CD99 antigen, is found in the pseudoautosomal region of both the X and Y chromosomes. Anti-Xg(a) is comparatively rare, and only two examples of anti-CD99 have ever been identified. Alloanti-Xg(a) is considered clinically insignificant; only one example of autoanti-Xg(a) has been reported, but it resulted in severe hemolytic anemia. Insufficient data exist to determine the clinical significance of anti-CD99. Linkage of XG to several X-borne genes encoding inherited disorders has been demonstrated. CD99 is an adhesion molecule, and high levels are associated with some types of cancer.