Structural basis for proapoptotic activation of Bak by the noncanonical BH3-only protein Pxt1.

Bak is a critical executor of apoptosis belonging to the Bcl-2 protein family. Bak contains a hydrophobic groove where the BH3 domain of proapoptotic Bcl-2 family members can be accommodated, which initiates its activation. Once activated, Bak undergoes a conformational change to oligomerize, which leads to mitochondrial destabilization and the release of cytochrome c into the cytosol and eventual apoptotic cell death. In this study, we investigated the molecular aspects and functional consequences of the interaction between Bak and peroxisomal testis-specific 1 (Pxt1), a noncanonical BH3-only protein exclusively expressed in the testis. Together with various biochemical approaches, this interaction was verified and analyzed at the atomic level by determining the crystal structure of the Bak-Pxt1 BH3 complex. In-depth biochemical and cellular analyses demonstrated that Pxt1 functions as a Bak-activating proapoptotic factor, and its BH3 domain, which mediates direct intermolecular interaction with Bak, plays a critical role in triggering apoptosis. Therefore, this study provides a molecular basis for the Pxt1-mediated novel pathway for the activation of apoptosis and expands our understanding of the cell death signaling coordinated by diverse BH3 domain-containing proteins.

Enhanced transfection efficiency of low generation PAMAM dendrimer conjugated with the nuclear localization signal peptide derived from herpesviridae.

Polyamidoamine (PAMAM) dendrimer is an extensively studied polymer in the biomedical research because of its low polydispersity, distinct molecular structure, and surface functionalities. Generally, a high-generational PAMAM dendrimer is used for gene delivery because transfection efficiency is dependent on charge density; however, an increase in charge density induces disruption of the cellular membrane, and damage to the membrane results in cytotoxicity. In this study, we selected PAMAM generation 2 to reduce the cytotoxic effect and conjugated RRILH and RRLHL sequences, nuclear localization signals (NLS) derived from herpesviridae to PAMAM generation 2. The transfection efficiency of RRILH-PAMAM G2 and RRLHL-PAMAM G2 was similar to that of polyethylenimine (PEI) in Neuro2A, HT22, and HaCaT cells, whereas their transfection efficiency was much higher than that of PEI in NIH3T3 cells. RRILH-PAMAM G2 showed relatively lower cytotoxicity than did RRLHL-PAMAM G2 in all cell lines, but the transfection capacity of the two polymers was similar. Our study shows that low-generational PAMAM dendrimer conjugated with NLS sequences has potential as an alternative to PEI in gene delivery.

Postoperative analgesic effects of ultrasound-guided transversus abdominis plane block for open appendectomy.

PURPOSE: Transversus abdominis plane (TAP) block is a newly developed and effective peripheral block involving the nerves of the anterior abdominal wall for lower abdominal surgery. We evaluated the postoperative analgesic efficacy of ultrasound-guided TAP block using 20 mL of 0.5% levobupivacaine in patients undergoing open appendectomy. METHODS: Forty-four patients undergoing appendectomy were assigned either to undergo a right sided-TAP block (group I, n = 22), or to receive standard care (group II, n = 22). All patients received standard anesthetics, and the TAP block group received ultrasound-guided right side TAP block using 20 mL of 0.5% levobupivacaine after induction of anesthesia. All patients received acetaminophen, and nonsteroidal anti-inflammatory drug as required during the 48 postoperative hours. Each patients was assessed for time to first rescue analgesia, verbal numerical rating pain scores (VNRS), number of rescue analgesic demands, nausea, vomiting, pruritus, and drowsiness by a blinded investigator at 0, 1, 3, 6, 12, 24 and 48 hours postoperatively. RESULTS: The TAP block group with levobupivacaine compared to the control group reduced VNRS significantly up to 12 hours postoperatively. There were no significant differences in time to first analgesia, number of rescue analgesics demands, nausea, vomiting, pruritus and drowsiness between the groups. There were no complications attributable to the TAP block. CONCLUSION: Ultrasound-guided TAP block using 20 mL of 0.5% levobupivacaine provided effective postoperative analgesia during the 12 postoperative hours after an open appendectomy.

Prevalence of fat embolism after total knee arthroplasty performed with or without computer navigation.

BACKGROUND: Total knee arthroplasty performed with computer-assisted navigation without breaching of the femoral medullary canal may decrease the prevalence of fat and/or bone-marrow-cell embolization. We performed this study to determine whether the use of navigation for primary total knee arthroplasty resulted in a different prevalence of fat and/or bone-marrow-cell embolization. METHODS: We enrolled 160 patients (210 knees) who were scheduled to undergo primary total knee arthroplasty with navigation and 160 patients (210 knees) who were scheduled to undergo primary total knee arthroplasty without navigation. Arterial and right atrial blood samples were obtained before insertion of a femoral alignment rod or cutting of the distal part of the femur (baseline); at one, three, five, and ten minutes after insertion of an alignment rod or cutting of the distal part of the femur; before insertion of a tibial component broach (baseline); at one, three, five, and ten minutes after insertion of a tibial component broach; and at twenty-four and forty-eight hours after the operation. We determined the presence of fat emboli and bone-marrow-cell emboli in histologic preparations of the blood samples. RESULTS: The prevalence of fat embolization was 49% (102 of 210 knees) in the total knee arthroplasty group managed with navigation and 52% (109 of 210 knees) in the total knee arthroplasty group managed without navigation (p = 0.2674). The prevalence of bone-marrow-cell embolization was 17% (thirty-six of 210 knees) in the group managed with navigation and 15% (thirty-one of 210 knees) in the group managed without navigation (p = 0.2591) CONCLUSIONS: The prevalence of fat and/or bone-marrow-cell embolization was not significantly different between the patients who underwent total knee arthroplasty with navigation and those who underwent it without navigation.