Amyloid precursor protein cytoplasmic domain antagonizes reelin neurite outgrowth inhibition of hippocampal neurons

The function of the amyloid precursor protein (APP), a key molecule in Alzheimer's disease (AD) remains unknown. Among the proteins that interact with the APP cytoplasmic domain in vitro and in heterologous systems is Disabled-1, a signaling molecule of the reelin pathway. The physiological consequence of this interaction is unknown. Here we used an in vitro model of hippocampal neurons grown on a reelin substrate that inhibits neurite outgrowth. Our results show that an excess of APP cytoplasmic domain internalized by a cell permeable peptide, is able to antagonize the neurite outgrowth inhibition of reelin. The APP cytoplasmic domain binds Disabled-1 and retains it in the cytoplasm, preventing it from reaching the plasma membrane and sequesters tyrosine phosphorylated Disabled-1, both of which disrupt reelin signaling. In the context of AD, increased formation of APP cytoplasmic domain in the cytosol released after cleavage of the A beta peptide, could then inhibit reelin signaling pathway in the hippocampus and thus influence synaptic plasticity.

Peri-pubertal maturation after developmental disturbance: a model for psychosis onset in the rat

Schizophrenia is thought to be associated with abnormalities during neurodevelopment although those disturbances usually remain silent until puberty; suggesting that postnatal brain maturation precipitates the emergence of psychosis. In an attempt to model neurodevelopmental defects in the rat, brain cellular proliferation was briefly interrupted with methylazoxymethanol (MAM) during late gestation at embryonic day 17 (E17). The litters were explored at pre- and post-puberty and compared with E17 saline-injected rats. We measured spontaneous and provoked locomotion, working memory test, social interaction, and prepulse inhibition (PPI). As compared with the saline-exposed rats, the E17 MAM-exposed rats exhibited spontaneous hyperactivity that emerged only after puberty. At adulthood, they also exhibited hypersensitivity to the locomotor activating effects of a mild stress and a glutamatergic N-methyl-D-aspartate receptor antagonist (MK-801), as well as PPI deficits whereas before puberty no perturbations were observed. In addition, spatial working memory did not undergo the normal peri-pubertal maturation seen in the sham rats. Social interaction deficits were observed in MAM rats, at both pre- and post-puberty. Our study further confirms that transient prenatal disruption of neurogenesis by MAM at E17 is a valid behavioral model for schizophrenia as it is able to reproduce some fundamental features of schizophrenia with respect to both phenomenology and temporal pattern of the onset of symptoms and deficits.

Pulmonary rehabilitation: analysis of a clinical service

BACKGROUND AND PURPOSE

There is significant research supporting the role of pulmonary rehabilitation in chronic obstructive pulmonary disease (COPD). However, less is known about real-life clinical rehabilitation services. Data were analysed from a clinical pulmonary rehabilitation service provided in the UK, consisting of seven weeks' twice-weekly training and education.

METHOD

A retrospective study. Baseline measures consisted of activity of daily living, mood state, spirometry, exercise tolerance using the Incremental Shuttle Walk Test (ISWT) and health status using the St George's Hospital Respiratory Questionnaire (SGRQ). Responders to pulmonary rehabilitation were defined as those with a mean reduction of four points on the SGRQ and a mean increase of 48 metres on the ISWT.

RESULTS

One hundred and eight patients entered the programme and 91 completed it. All outcomes showed statistically and clinically significant change after the rehabilitation programme. Responder analysis showed that 37% of patients achieved benefits for both the SGRQ and the ISWT. Twenty-eight per cent of patients were non-responders for both; 17% benefited for the SGRO only and 14% improved their exercise tolerance. Patients with restrictive disease (n = 11) showed large mean ISWT score of 98.2 m (Standard deviation (SD) 69.4 m) (p < 0.01), as did patients with moderate COPD (n = 30), who scored a mean ISWT change of 77.3 m (SD 92.0 m) (p < 0.01) and a SGRQ score of -7.6 (SD 13.7) (p < 0.01), and those with mild COPD (n = 12), who scored a mean ISWT change of 62.5 m (SD 87.4 m) (p < 0.01) and a mean SGRQ change of -3. 7 (SD 8.1) (p < 0.01). Patients with severe COPD (n = 23) showed a smaller mean change in ISWT of 32.6 m (SD 79.4 m) and in SGRQ of -2.8 (SD 7.1). However, analysis of variance (ANOVA) showed no statistical differences between the groups (p = 0.13).

CONCLUSIONS

Clinical pulmonary rehabilitation programmes are effective for most patients. However for patients with more severe impairment, maximal gains may be harder, or take longer, to achieve. Patients with restrictive disease appear to do well, although future trials will be needed to test this supposition.