Outcomes in Combined Anterior and Posterior Fusion for 3- and 4-Level Degenerative Lumbar Disc Disease

Introduction. This study reported the clinical and functionaloutcomes in a consecutive series of patients with3- or 4-level degenerative disc disease (DDD) betweenvertebral levels L2 to S1, who were treated with combinedanterior lumbar interbody fusion (ALIF) and posteriorspinal fusion at one-year and two-year follow-ups. Methods. A retrospective chart review was performed on allpatients who underwent long segment fusion for DDD by asingle surgeon between August 2002 and January 2012. Fiftyfivepatients were identified and 32 had complete charts for review(14 had one-year follow-up and 18 two-year follow-up).In addition to demographic data, disability (Oswestry DisabilityIndex, ODI), pain level (Visual Analog Scale, VAS), andflexion-extension range-of-motion were measured pre- andpost-operatively. Operative data also were collected, includingoperative time, blood loss, surgical implants used, surgicalapproach, operative levels treated, and complications.Results. Both VAS and ODI improved significantly postoperatively.The average VAS score improved from 6.5 ± 1.5(range: 4 - 9) to 4.4 ± 1.7 (range: 2 - 7) for one-year follow-up,and 7.0 ± 1.8 (range: 4 - 10) to 4.4 ± 2.6 (range: 1 - 9) for twoyearfollow-up. For one-year follow-up, the average ODI scoreimproved from 53 ± 19% (range: 18 - 70%) to 37 ± 17% (range:12 - 64%), and for two-year follow-up, the average improvedfrom 53 ± 18% (range: 18 - 80%) to 31 ± 24% (range: 2 - 92%).The level of improvement in pain and function was similar topreviously published data for 1- and 2-level fusions, but overallpain and function scores were worse in this study group. Conclusions. Arthrodesis for 3- and 4-level DDD is, on average,a successful surgery that shows clinically significantimprovements in function and pain similar to fusionfor 1- and 2-levels with low rates of re-operation. Patientswith involvement of 3- or 4-levels have higher disabilityand pain both pre- and post-operatively compared to shorterfusion level involvement. KS J Med 2016;9(3):50-53

The crystal structure of pyruvate decarboxylase from Kluyveromyces lactis. Implications for the substrate mechanism of this enzyme.

The crystal structure of pyruvate decarboxylase from Kluyveromyces lactis has been determined to 2.26 A resolution. Like other yeast enzymes, Kluyveromyces lactis pyruvate decarboxylase is subject to allosteric substrate activation. Binding of substrate at a regulatory site induces catalytic activity. This process is accompanied by conformational changes and subunit rearrangements. In the nonactivated form of the corresponding enzyme from Saccharomyces cerevisiae, all active sites are solvent accessible due to the high flexibility of loop regions 106-113 and 292-301. The binding of the activator pyruvamide arrests these loops. Consequently, two of four active sites become closed. In Kluyveromyces lactis pyruvate decarboxylase, this half-side closed tetramer is present even without any activator. However, one of the loops (residues 105-113), which are flexible in nonactivated Saccharomyces cerevisiae pyruvate decarboxylase, remains flexible. Even though the tetramer assemblies of both enzyme species are different in the absence of activating agents, their substrate activation kinetics are similar. This implies an equilibrium between the open and the half-side closed state of yeast pyruvate decarboxylase tetramers. The completely open enzyme state is favoured for Saccharomyces cerevisiae pyruvate decarboxylase, whereas the half-side closed form is predominant for Kluyveromyces lactis pyruvate decarboxylase. Consequently, the structuring of the flexible loop region 105-113 seems to be the crucial step during the substrate activation process of Kluyveromyces lactis pyruvate decarboxylase

Purification, biosynthesis and cellular localization of a major 125-kDa glycophosphatidylinositol-anchored membrane glycoprotein of Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae has been shown to contain a major 125-kDa membrane glycoprotein which is anchored in the lipid bilayer by a glycophosphatidylinositol anchor. This protein was purified to near homogeneity and was used to raise a rabbit antibody. Biosynthesis of the 125-kDa protein was studied by immunoprecipitation of 35SO4-labeled material from wild-type cells or a secretion mutant (sec18) in which the vesicular traffic from the endoplasmic reticulum (ER) to the Golgi is blocked. The 125-kDa protein is first made in the ER as a 105-kDa precursor which already contains a glycophosphatidylinositol anchor and which is slowly transformed into the 125-kDa form upon chase (t1/2 approximately 10-15 min). The 105-kDa precursor can be reduced to an 83-kDa form by the enzymatic removal of N-glycans. The removal of N-glycans from the mature 125-kDa protein yields a 95-kDa species. Thus, removal of the N-glycans does not reduce the ER and mature forms to the same molecular mass, indicating that not only elongation of N-glycans but also another post-translational modification takes place during maturation. Selective tagging of surface proteins by treatment of 35SO4-labeled cells with trinitrobenzene sulfonic acid at 0 C followed by immunoprecipitation of the tagged proteins shows that the 125-kDa protein, but not the 105-kDa precursor, becomes transported to the cell surface. This tagging of cells after various lengths of chase also shows that the surface appearance of the protein is biphasic with about one half of the mature 125-kDa protein remaining intracellular for over 2 h. Glycosylation and/or glycophosphatidylinositol anchor addition is important for the stability of the 125-kDa protein since the protein remains undetectable in sec53, a temperature-sensitive mutant which does not make GDP-mannose at 37 C and does not add glycophosphatidylinositol anchors at 37 degrees C