Molecular diversity of arbuscular mycorrhizal fungi and patterns of host association over time and space in a tropical forest.

We have used molecular techniques to investigate the diversity and distribution of the arbuscular mycorrhizal (AM) fungi colonizing tree seedling roots in the tropical forest on Barro Colorado Island (BCI), Republic of Panama. In the first year, we sampled newly emergent seedlings of the understory treelet Faramea occidentalis and the canopy emergent Tetragastris panamensis, from mixed seedling carpets at each of two sites. The following year we sampled surviving seedlings from these cohorts. The roots of 48 plants were analysed using AM fungal-specific primers to amplify and clone partial small subunit (SSU) ribosomal RNA gene sequences. Over 1300 clones were screened for random fragment length polymorphism (RFLP) variation and 7% of these were sequenced. Compared with AM fungal communities sampled from temperate habitats using the same method, the overall diversity was high, with a total of 30 AM fungal types identified. Seventeen of these types have not been recorded previously, with the remainder being similar to types reported from temperate habitats. The tropical mycorrhizal population showed significant spatial heterogeneity and nonrandom associations with the different hosts. Moreover there was a strong shift in the mycorrhizal communities over time. AM fungal types that were dominant in the newly germinated seedlings were almost entirely replaced by previously rare types in the surviving seedlings the following year. The high diversity and huge variation detected across time points, sites and hosts, implies that the AM fungal types are ecologically distinct and thus may have the potential to influence recruitment and host composition in tropical forests.

Laparoscopic versus open appendicectomy for suspected appendicitis: a prospective study.

Despite recent advances in minimally invasive surgery, laparoscopic appendicectomy has been questioned as a feasible method of treating patients with suspected appendicitis because open appendicectomy carries few risks and complications. Between February 1992 and January 1993 a non-randomized prospective study comparing open and laparoscopic appendicectomy was designed to assess differences in postoperative morbidity, pain, inpatient hospital stay and a return to normal lifestyle. One hundred and sixty-seven patients with suspected clinical appendicitis were assigned to open (n = 74) or laparoscopic (n = 93) appendicectomy. Six patients were excluded due to the presence of other significant pathology such that the appendix was not removed. Eighty-seven patients underwent attempted laparoscopic appendicectomy, of which 81 were completed. The diagnosis of appendicitis was confirmed histologically in 63.5% of patients undergoing open appendicectomy and 63% of patients undergoing laparoscopic appendicectomy. There were no significant differences in anaesthetic times, postoperative morbidity and analgesic requirements. There was a significant reduction in both postoperative inpatient stay (P < 0.0001) and time taken to return to work or normal activities (P < 0.0001) for the laparoscopic group. The use of laparoscopy for patients with suspected appendicitis aids definitive diagnosis and should reduce the negative appendicectomy rate to an acceptable figure. The results suggest that laparoscopic appendicectomy is safe and offers advantages over open appendicectomy in the management of patients with suspected appendicitis.

Obstruction of the gastrointestinal tract by foreign bodies in adults.

Foreign bodies may become impacted because of congenital or acquired narrowing of the gastrointestinal tract or owing to unusual physical characteristics of the ingested material. Active intervention is necessary when impaction is complicated by intestinal obstruction or perforation or when the foreign body is composed of a toxic substance.