Descubren una clave del estrés celular, un defecto en la producción de proteínas

The unfolded protein response triggers selective mRNA release from the endoplasmic reticulum.

Abstract

The unfolded protein response (UPR) is a stress response program that reprograms cellular translation and gene expression in response to proteotoxic stress in the endoplasmic reticulum (ER). One of the primary means by which the UPR alleviates this stress is by reducing protein flux into the ER via a general suppression of protein synthesis and ER-specific mRNA degradation. We report here an additional UPR-induced mechanism for the reduction of protein flux into the ER, where mRNAs that encode signal sequences are released from the ER to the cytosol. By removing mRNAs from the site of translocation, this mechanism may serve as a potent means to transiently reduce ER protein folding load and restore proteostasis. These findings identify the dynamic subcellular localization of mRNAs and translation as a selective and rapid regulatory feature of the cellular response to protein folding stress. 

Algunos cerebros parecen compensar la acumulación de proteína β-amiloide

Neural compensation in older people with brain amyloid-β deposition

Recruitment of extra neural resources may allow people to maintain normal cognition despite amyloid-β (Aβ) plaques. Previous fMRI studies have reported such hyperactivation, but it is unclear whether increases represent compensation or aberrant overexcitation. We found that older adults with Aβ deposition had reduced deactivations in task-negative regions, but increased activation in task-positive regions related to more detailed memory encoding. The association between higher activity and more detailed memories suggests that Aβ-related hyperactivation is compensatory.

Nueva técnica de ‘puenteo’ neural para hacer llegar órdenes a las piernas de personas con lesiones medulares

Volitional walking via upper limb muscle-controlled stimulation of the lumbar locomotor center in man.

Abstract

Gait disturbance in individuals with spinal cord lesion is attributed to the interruption of descending pathways to the spinal locomotor center, whereas neural circuits below and above the lesion maintain their functional capability. An artificial neural connection (ANC), which bridges supraspinal centers and locomotor networks in the lumbar spinal cord beyond the lesion site, may restore the functional impairment. To achieve an ANC that sends descending voluntary commands to the lumbar locomotor center and bypasses the thoracic spinal cord, upper limb muscle activity was converted to magnetic stimuli delivered noninvasively over the lumbar vertebra. Healthy participants were able to initiate and terminate walking-like behavior and to control the step cycle through an ANC controlled by volitional upper limb muscle activity. The walking-like behavior stopped just after the ANC was disconnected from the participants even when the participant continued to swing arms. Furthermore, additional simultaneous peripheral electrical stimulation to the foot via the ANC enhanced this walking-like behavior. Kinematics of the induced behaviors were identical to those observed in voluntary walking. These results demonstrate that the ANC induces volitionally controlled, walking-like behavior of the legs. This paradigm may be able to compensate for the dysfunction of descending pathways by sending commands to the preserved locomotor center at the lumbar spinal cord and may enable individuals with paraplegia to regain volitionally controlled walking. 

Un estudio relaciona el uso a largo plazo de benzodiacepinas con la enfermedad de Alzheimer

Benzodiazepine use and risk of Alzheimer’s disease: case-control study

Abstract

Objectives To investigate the relation between the risk of Alzheimer’s disease and exposure to benzodiazepines started at least five years before, considering both the dose-response relation and prodromes (anxiety, depression, insomnia) possibly linked with treatment.

Design Case-control study.

Setting The Quebec health insurance program database (RAMQ).

Participants 1796 people with a first diagnosis of Alzheimer’s disease and followed up for at least six years before were matched with 7184 controls on sex, age group, and duration of follow-up. Both groups were randomly sampled from older people (age >66) living in the community in 2000-09.

Main outcome measure The association between Alzheimer’s disease and benzodiazepine use started at least five years before diagnosis was assessed by using multivariable conditional logistic regression. Ever exposure to benzodiazepines was first considered and then categorised according to the cumulative dose expressed as prescribed daily doses (1-90, 91-180, >180) and the drug elimination half life.

Results Benzodiazepine ever use was associated with an increased risk of Alzheimer’s disease (adjusted odds ratio 1.51, 95% confidence interval 1.36 to 1.69; further adjustment on anxiety, depression, and insomnia did not markedly alter this result: 1.43, 1.28 to 1.60). No association was found for a cumulative dose <91 1.74="" 1.84="" 2.08="" 91-180="" and="" association="" daily="" density="" doses.="" doses="" exposure="" for="" increased="" of="" prescribed="" strength="" the="" to="" with="">180 prescribed daily doses) and with the drug half life (1.43 (1.27 to 1.61) for short acting drugs and 1.70 (1.46 to 1.98) for long acting ones).

Conclusion Benzodiazepine use is associated with an increased risk of Alzheimer’s disease. The stronger association observed for long term exposures reinforces the suspicion of a possible direct association, even if benzodiazepine use might also be an early marker of a condition associated with an increased risk of dementia. Unwarranted long term use of these drugs should be considered as a public health concern.