The giant protein AHNAK involved in morphogenesis and laminin substrate adhesion of myelinating Schwann cells.

Within the nervous system, expression of the intriguing giant protein AHNAK had been reported so far only for blood-brain barrier forming vascular endothelium. In a screen for genes upregulated after spinal cord injury, we recently identified ahnak as being highly expressed by non-neuronal cells invading the lesion, delimiting the interior surface of cystic cavities in front of barrier-forming astrocytes. Here, we show for the first time that AHNAK is constitutively expressed in peripheral nervous system, notably by myelinating Schwann cells (SCs), in which we investigated its function. During sciatic nerve development, AHNAK is redistributed from adaxonal toward abaxonal SC compartments in contact with basement membrane. AHNAK labeling on myelinated fibers from adult nerve delineates the so-called "Cajal bands," constituting the residual peripheral SC cytoplasm. Its distribution pattern is complementary to that of periaxin, known to be involved in the myelination process. In vitro, nonconfluent cultured primary SCs seeded on laminin express high levels of AHNAK concentrated in their processes, whereas at confluence, AHNAK is downregulated together with laminin receptor dystroglycan. AHNAK silencing by siRNA interference affects SC morphology and laminin-substrate attachment, as well as expression and distribution of dystroglycan. Thus, our results clearly show the implication of AHNAK in SC adhesion to laminin, probably via targeting of the dystroglycan-associated receptor complex. These findings are of high interest regarding the importance of SC-basal lamina interactions for myelination and myelin maintenance, and open up new perspectives for investigations of the molecular mechanisms underlying demyelinating neuropathies.

Adolescence/adult onset MTHFR deficiency may manifest as isolated and treatable distinct neuro-psychiatric syndromes.

5,10-Methylene-tetrahydrofolate reductase (MTHFR) deficiency is a genetic disorder that can occur at any age and can be easily detected by increased homocysteinemia. In adolescence/adult onset forms, the clinical picture is often complex with association of various neurological features and thrombosis.Here we report the cases of two adult siblings who experienced focal epilepsy at 18 years old as a first disease manifestation, without other symptom during several years. Upon diagnosis, both patients received metabolic treatment comprising B9, B12 and betaine which has stopped the occurrence of seizures, allowing discontinuation of anti-epileptic drugs.Among 24 reviewed adolescent/adult onset patients with MTHFR deficiency in the literature, clinical manifestations included gait disorder (96%, from motor central or peripheral origin), cognitive decline (74%), epileptic syndromes (50%), encephalopathy (30%), psychotic symptoms (17%), and thrombotic events (21%). A total of 41% presented a single neurological manifestation that could stay isolated during at least 3 years, delaying achievement of the diagnosis. Brain MRI showed a mostly periventricular white matter changes in 71% of cases. All patients stabilized or improved following metabolic treatment.Despite being rare, adolescence/adult onset MTHFR deficiency can nevertheless be successfully treated. Therefore, homocysteinemia should be tested in various unexplained neuro-psychiatric syndromes like epilepsy or spastic paraparesis, even if isolated, since waiting for completion of the clinical picture is likely to increase the risk of irreversible neurological damage.

Extensive structural remodeling of the injured spinal cord revealed by phosphorylated MAP1B in sprouting axons and degenerating neurons.

Spinal cord injury (SCI) results in loss of sensory and motor function because injured axons do not regenerate and neurons that die are not replaced. Nevertheless, there is evidence for spontaneous reorganization of spared pathways (i.e. sprouting) that could be exploited to improve functional recovery. The extent of morphological remodeling after spinal cord injury is, however, not understood. We have previously shown that a phosphorylated form of microtubule-associated protein-1B, MAP1B-P, is expressed by growing axons, but is detected in intact adult SC in fibers exhibiting a somatotopic distribution of myelinated sensory fibers. We now demonstrate that after adult SCI, MAP1B-P is up-regulated in other classes of axons. We used immunohistochemistry to show changing levels and distributions of MAP1B-P after a right thoracic hemisection of adult rat spinal cord. MAP1B-P labeling suggests rearrangements of the axonal circuitry that go well beyond previous descriptions. MAP1B-P-positive fibers are present in ectopic locations in gray matter in both dorsal and ventral horns and around the central canal. Double staining reveals that primary sensory and descending serotonergic and corticospinal axons are MAP1B-P positive. In white matter, high MAP1B-P expression is found on terminal enlargements near the injury, reflecting retraction of transected axons. MAP1B-P also accumulates in pre-apoptotic neuronal somata axotomized by the lesion, indicating association of MAP1B-P not only with axon extension and retraction, but also with neuronal degeneration. Finally, we provide evidence that MAP1B phosphorylation is correlated with activation of JNK MAP-kinase, providing a step towards unraveling the mechanisms of regulation of this plasticity-related cytoskeletal protein.

Spinal cord injury-induced up-regulation of AHNAK, expressed in cells delineating cystic cavities, and associated with neoangiogenesis.

To investigate the molecular basis for the poor regenerative capacity of the mammalian central nervous system (CNS) after injury, we searched for genes whose expression was affected by an adult rat spinal cord hemi-section. Differential screening of a rat spinal cord expression library was performed using polyclonal antibodies raised against lesioned spinal cord tissue. A striking overexpression was found for ahnak, encoding a 700-kDa protein, in normal CNS present only in the blood-brain barrier (BBB) forming vascular endothelial cells. Indeed, very early after spinal cord injury (SCI), high levels of membrane-associated AHNAK are observed on non-neuronal cells invading the lesion site. With time, AHNAK distribution spreads rostrally and caudally concomitant with the process of tissue inflammation and axon degeneration, delineating the interior surface of cystic cavities, mainly in front of barrier-forming astrocytes. Strong overexpression is also observed on vascular endothelial cells reacting to BBB breakdown. Based on our detailed analysis of its spatiotemporal and cellular expression, and its previously described function in BBB, we suggest that AHNAK expression is associated with cell types displaying tissue-protective barrier properties. Our study may thus contribute to the elucidation of the precise molecular and cellular events that eventually render traumatic spinal cord tissue non-permissive for regeneration.

Morfologia da Acta Cirúrgica Brasileira normas e exigências para a publicaçäo / Morphology of the journal Acta Cirúrgica Brasileira: guidelines for the format of manuscripts for publication

Apresenta-se o estilo da Acta Cirúrgica Brasileira e as características para a elaboraçäo de artigos científicos conforme o estilo Vancouver. Recomenda-se a leitura atenta das Instruçöes aos Autores. Ressalta-se os critérios de avaliaçäo dos artigos. Destaca-se o cumprimento das normas do Comitê Internacional dos Editores de Revistas Médicas.

Efeito da n-acetilcisteína no pulmäo após isquemia hepática em ratos / Effect of n-acetilcysteine in lungs after liver ischemia in rats

Na síndrome de isquemia e reperfusäo os pulmöes podem ser alvo de lesäo a distância como nos casos de choque, trauma ou ainda nos casos de transplante hepático. Objetivo: Avaliar o efeito protetor da N-acetilcisteína (NAC) sobre os pulmöes após isquemia hepática. Métodos: Foram utilizados 12 ratos, machos, linhagem EPM-1 Wistar, separados aleatoriamente em dois grupos com seis animais (controle e experimento). Os animais de ambos os grupos foram submetidos à anestesia com cloridrato de quetamina e cloridrato de xilazina. Realizou-se a incisäo mediana longitudinal, identificaçäo do hilo hepático e da veia cava caudal. Quinze minutos antes do clampeamento injetou-se soluçäo glicosada a 5 por cento no grupo controle e NAC diluída em soluçäo glicosada a 5 por cento no grupo experimento. Os animais foram mantidos em isquemia hepática durante 30 minutos, sendo em seguida realizada toracotomia e remoçäo cirúrgica dos pulmöes para avaliaçäo histológica com coloraçäo pela hematoxilina-eosina. Resultados: A análise dos cortes do parênquima pulmonar mostrou semelhança nos dois grupos estudados, ocorrendo colapso alveolar, infiltrado neutrofilico, congestäo vascular e áreas hemorrágicas, compatíveis com a repercussäo sistêmica da isquemia hepática. Conclusäo: A NAC näo modifica a lesäo pulmonar decorrente da isquemia, à microscopia óptica.