The effect of prolonged monocular occlusion on latent nystagmus in the treatment of amblyopia

We recorded eye movements in 5 patients with latent nystagmus (LN) before and after 2 days of occlusion of the better eye. The slow-phase speed of the nystagmus (SPS) was in general, before occlusion, lower when the better eye fixated but, after occlusion, lower when the worse eye fixated. However, the sum of SPS during right fixation and SPS during left fixation remained constant. Oscillopsia complaints gradually disappeared during the period of occlusion. These findings indicate that the difference between the SPS during fixation with the right eye and the SPS during fixation with the left eye in LN patients is caused by a compensatory drift that decreases LN during fixation with the better eye but increases LN during fixation with the worse eye. During occlusion, this compensatory drift changes its direction and magnitude slowly over days. Hence, occlusion of the better eye in children with amblyopia and LN should be prescribed only in days per week, not in hours per day

Expression analysis of Clavata1-like and Nodulin21-like genes from Pinus sylvestris during ectomycorrhiza formation

The ecology and physiology of ectomycorrhizal (EcM) symbiosis with conifer trees are well documented. In comparison, however, very little is known about the molecular regulation of these associations. In an earlier study, we identified three EcM-regulated Pinus expressed sequence tags (EST), two of which were identified as homologous to the Medicago truncatula nodulin MtN21. The third EST was a homologue to the receptor-like kinase Clavata1. We have characterized the expression patterns of these genes and of auxin- and mycorrhiza-regulated genes after induction with indole-3-butyric acid in Pinus sylvestris and in a time course experiment during ectomycorrhizal initiation with the co-inoculation of 2,3,5-triiodobenzoic acid, an auxin transport inhibitor. Our results suggest that different P. sylvestris nodulin homologues are associated with diverse processes in the root. The results also suggest a potential role of the Clv1-like gene in lateral root initiation by the ectomycorrhizal fungus

Analysis of two methods of isometric muscle contractions during the anti-G straining maneuver

This study investigated the difference in Mean Arterial Pressure (MAP) and Cardiac Output (CO) between two methods of isometric muscle contractions during the Anti-G Straining Maneuver (AGSM). 12 subjects (ages 18 to 38 yrs, height 176.8 +/- 7.4 cm, body mass 78.8 +/- 15.6 kg, percent body fat 14.3 +/- 6.6%) participated in the study. The study was a one-way within-subject design with test conditions counterbalanced. Two methods of isometric muscle contractions lasting 30 seconds each were assessed; an isometric push contraction and an isometric muscle tensing contraction. The dependent parameters were MAP and CO. The average MAP during the push contraction was 123 mmHg, SD +/- 11 and for tense was 118 mmHg, SD +/- 8. CO was 7.6 L/min, SD +/- 1.6 for push and 7.9 L/min, SD +/- 2.0 for tense method. Dependent t-tests revealed t(11) = 1.517, p = 0.157 for MAP and t(11) = 0.875, p = 0.400 for CO. This study demonstrated that the two methods of isometric muscle contractions were not statistically different with regards to MAP and CO. Therefore, both forms of isometric contractions may be potentially useful when performing the muscle contraction portion of the AGSM

Can human amblyopia be treated in adulthood?

Amblyopia is a common visual disorder that results in a spatial acuity deficit in the affected eye. Orthodox treatment is to occlude the unaffected eye for lengthy periods, largely determined by the severity of the visual deficit at diagnosis. Although this treatment is not without its problems (poor compliance, potential to reduce binocular function, etc) it is effective in many children with moderate to severe amblyopia. Diagnosis and initiation of treatment early in life are thought to be critical to the success of this form of therapy. Occlusion is rarely undertaken in older children (more than 10 years old) as the visual benefits are considered to be marginal. Therefore, in subjects where occlusion is not effective or those missed by mass screening programs, there is no alternative therapy available later in life. More recently, burgeoning evidence has begun to reveal previously unrecognized levels of residual neural plasticity in the adult brain and scientists have developed new genetic, pharmacological, and behavioral interventions to activate these latent mechanisms in order to harness their potential for visual recovery. Prominent amongst these is the concept of perceptual learning—the fact that repeatedly practicing a challenging visual task leads to substantial and enduring improvements in visual performance over time. In the normal visual system the improvements are highly specific to the attributes of the trained stimulus. However, in the amblyopic visual system, learned improvements have been shown to generalize to novel tasks. In this paper we ask whether amblyopic deficits can be reduced in adulthood and explore the pattern of transfer of learned improvements. We also show that developing training protocols that target the deficit in stereo acuity allows the recovery of normal stereo function even in adulthood. This information will help guide further development of learning-based interventions in this clinical group