Dystroglycan mediates homeostatic synaptic plasticity at GABAergic synapses.

Dystroglycan (DG), a cell adhesion molecule well known to be essential for skeletal muscle integrity and formation of neuromuscular synapses, is also present at inhibitory synapses in the central nervous system. Mutations that affect DG function not only result in muscular dystrophies, but also in severe cognitive deficits and epilepsy. Here we demonstrate a role of DG during activity-dependent homeostatic regulation of hippocampal inhibitory synapses. Prolonged elevation of neuronal activity up-regulates DG expression and glycosylation, and its localization to inhibitory synapses. Inhibition of protein synthesis prevents the activity-dependent increase in synaptic DG and GABAA receptors (GABAARs), as well as the homeostatic scaling up of GABAergic synaptic transmission. RNAi-mediated knockdown of DG blocks homeostatic scaling up of inhibitory synaptic strength, as does knockdown of like-acetylglucosaminyltransferase (LARGE)--a glycosyltransferase critical for DG function. In contrast, DG is not required for the bicuculline-induced scaling down of excitatory synaptic strength or the tetrodotoxin-induced scaling down of inhibitory synaptic strength. The DG ligand agrin increases GABAergic synaptic strength in a DG-dependent manner that mimics homeostatic scaling up induced by increased activity, indicating that activation of this pathway alone is sufficient to regulate GABAAR trafficking. These data demonstrate that DG is regulated in a physiologically relevant manner in neurons and that DG and its glycosylation are essential for homeostatic plasticity at inhibitory synapses.

Preventing the preventable: role of transamine in total knee arthroplasty.

OBJECTIVE: To assess the efficacy and safety of perioperative intravenous Tranexamic Acid in reducing blood loss and transfusion requirements in patients undergoing Total Knee Arthroplasty. METHODS: The prospectivedouble-blind randomised control trial was conducted from March to July 2014 at the Combined Military Hospital, Rawalpindi, and comprised patients below 85 years of age undergoing unilateral or bilateral cemented Total Knee Arthroplasty. The patients were divided into control or Transaminegroups. Two doses of 15mg/kg of Transamine were given to the latter group. All patients were operated under spinal or combined spinal-epidural anaesthesiausing pneumatic tourniquet and similar cemented implant. Primary outcome was postoperative blood loss in drains. Secondary outcomes were the number of blood units transfused, change in haemoglobin level and adverse events. RESULTS: Of the 62 patients on the study, there were 34(55%) patents in the Transaminegroup with a mean age of 64±8.4 years, and28(45%)in the control group with a mean age of 60.8±10.3. The two groups were matched for demographic and blood indices.Mean blood loss via intra-articular drain in the control group was 619±243ml per knee, and 402±169ml per knee in the Transaminegroup. Blood transfusions were required by 14(50%)patients in the control groupand 6(17.6%)in the Transaminegroup. CONCLUSIONS: Perioperative intravenous transamine significantly reduced blood loss as well as blood transfusion requirements.

Integrins regulate centrosome integrity and astrocyte polarization following a wound.

In response to a wound, astrocytes in culture extend microtubule-rich processes and polarize, orienting their centrosomes and Golgi apparatus woundside. ß1 Integrin null astrocytes fail to extend processes toward the wound, and are disoriented, and often migrate away orthogonal, to the wound. The centrosome is unusually fragmented in ß1 integrin null astrocytes. Expression of a ß1 integrin cDNA in the null background yields cells with intact centrosomes that polarize and extend processes normally. Fragmented centrosomes rapidly assemble following integrin ligation and cell attachment. However, several experiments indicated that cell adhesion is not necessary. For example, astrocytes in suspension expressing a chimeric ß1 subunit that can be activated by an antibody assemble centrosomes suggesting that ß1 activation is sufficient to cause centrosome assembly in the absence of cell adhesion. siRNA knockdown of PCM1, a major centrosomal protein, inhibits cell polarization, consistent with the notion that centrosomes are necessary for polarity and that integrins regulate polarity via centrosome integrity. Screening inhibitors of molecules downstream of integrins indicate that neither FAK nor ILK is involved in regulation of centrosome integrity. In contrast, blebbistatin, a specific inhibitor of non-muscle myosin II (NMII), mimics the response of ß1 integrin null astrocytes by disrupting centrosome integrity and cell polarization. Blebbistatin also inhibits integrin-mediated centrosome assembly in astrocytes attaching to fibronectin, consistent with the hypothesis that NMII functions downstream of integrins in regulating centrosome integrity.