To achieve a better understanding of learning and declarative memory under mild transient stress, we investigated the effect of brief hypobaric hypoxia on spatial orientation in rats. Young male Wistar rats aged 30 days were exposed for 60 min to hypobaric hypoxia, simulating an altitude of 7000 m (23 000 ft) either shortly prior to attempting or after mastering an allothetic navigation task in the Morris water maze with a submerged platform. The post-hypoxic group performed significantly better in the navigation task than the control animals (the mean difference in escape latencies was 11 seconds; P= 0.0033, two-way ANOVA with repeated measures, group × session). The experimental group also achieved a remarkably higher search efficiency (calculated as a percentage of su
ccessful trials per session), especially during the first four days following hypoxic stress (P= 0.0018). During the subsequent training, the post-hypoxic group performed better than the control animals, whilst the efficiency levels of both groups progressively converged. Spatial memory retention and recall of well-trained rats were not affected by the transient hyp
obaric hypoxia. These results indicate that brief hypobaric hypoxia enhances rats’ spatial orientation. Our findings are consistent with several studies, which also suggested that mild transient stress improves learning.
This paper summarizes work done in this laboratory over the last two years on the cloning of microsporidian rRNA by homology PCR and its subsequent use in diagnostic tests and phylogenetic studies. Using highly conserved primers in the 16S or small subunit rRNA (SSU-rRNA) these genes were cloned from human intestinal biopsies with transmission electron microscopy proven Enterocytozoon bieneusi and Septata intestinalis. The SSU-rRNA genes were then used to design and test several primer pairs for the diagnosis of microsporidian infection. Utilizing the polymerase chain reaction and primers V1 and EB45Ü Ent. bieneusi infected duodenal aspirates or intestinal biopsies could be detected. Using V I and SI500 infection with S. intestinalis could be detected. In addition to diagnostic tests, phylogenetic relationships were examined using sequence data from the fragment amplified by PCR by primer 530f in the SSU-rRNA and primer 580r in the large subunit rRNA. This data supported the placement of S. intestinalis in the family Encephalitozoonidae. In addition, it confirmed that Encephalitozoon cuniculi, E. hellem and S. intestinalis are distinct organisms. These techniques have broad applications to the study of other microsporidia and the development of a molecular phylogeny.