[Bilateral central femoral dislocation after seizure. Antiprotrusive ring and dual mobility cup as a therapeutic option. Apropos of a case]. / Luxación bilateral central femoral tras crisis convulsiva. Anillo antiprotrusivo y cotilo de doble movilidad como opción terapéutica. A propósito de un caso.

INTRODUCTION: seizures can trigger fractures and dislocations. Injuries depend on the severity, duration and type of seizure. We present a case report of a male patient who presented with a bilateral central dislocation fracture of the hip following an episode of seizure. A case rarely described in the literature with complex and unusual management. CASE REPORT: a 77-year-old man with a history of moderate cognitive impairment suffered a bilateral central dislocation of the hip in the context of a generalized epileptic seizure. Clinically on arrival at the emergency department, the patient presented shortening of the right lower extremity compared to the contralateral, external rotation and joint locking on log roll test in both extremities. An imaging study and clinical optimization were performed prior to surgery. It was performed in two stages. First the left hip on the 8th day of admission, and the right hip on the 15th. In both surgeries the same procedure was performed, with implantation of an antiprotrusive ring and a double mobility cup prosthesis with an uncemented femoral stem. In the immediate postoperative period, the patient did not present any complications associated with the surgery. At 24-month follow-up, the patient performed full weight bearing with a Harris hip score (HHS) of 77 on the right hip and 79 on the left; 12 points on the WOMAC scale. No postoperative complications have occurred so far. CONCLUSIONS: these injuries are uncommon in our daily practice, where multiple options are available to address them. In our patient, the use of arthroplasty and antiprotrusive rings offers advantages over fracture synthesis techniques, such as early mobilization with moderate functional results and few postoperative complications.

INTRODUCCIÓN: las crisis convulsivas pueden desencadenar fracturas y luxaciones. Las lesiones dependen de la severidad, duración y el tipo de crisis. Presentamos un caso clínico de un varón que presentó una fractura luxación central bilateral de cadera tras episodio de crisis convulsiva. Un caso pocas veces descrito en la literatura con un manejo complejo y poco habitual. CASO CLÍNICO: paciente de 77 años con antecedentes de deterioro cognitivo moderado que sufrió una luxación bilateral central de cadera en contexto de una crisis convulsiva generalizada. Clínicamente, a su llegada a urgencias, el paciente presentaba un acortamiento de la extremidad inferior derecha en comparación con la contralateral, rotación externa y bloqueo articular a la realización del log roll test en ambas extremidades. Se realizó estudio de imagen y optimización clínica previo a cirugía. Se realizó en dos tiempos: primero la cadera izquierda al octavo día de ingreso y la cadera derecha al decimoquinto. En ambas cirugías se realizó el mismo procedimiento mediante implantación de anillo antiprotrusivo y prótesis con cotilo de doble movilidad con vástago femoral no cementado. En el postoperatorio inmediato, el paciente no presentó ninguna complicación asociada a la cirugía. En el seguimiento a los 12 meses, el paciente realiza carga completa con un Harris hip score (HHS) de 77 cadera derecha y 79 en la izquierda; 12 puntos en la escala WOMAC. No ha presentado complicaciones postoperatorias hasta el momento. CONCLUSIONES: estas lesiones son poco comunes en nuestra práctica diaria, donde disponemos de múltiples opciones para abordarlas. En nuestro paciente, el empleo de la artroplastía y de anillos antiprotrusivos nos ofrecen ventajas respecto a las técnicas de síntesis de la fractura, como una movilización precoz y evitar desarrollo prematuro de una artrosis postraumática, con resultados buenos, funcionales y pocas complicaciones postoperatorias.

[Evolution of blood loss in total knee prosthesis with blood recovery system vs conventional drainage]. / Evolución de la pérdida sanguínea en la prótesis total de rodilla con recuperador de sangre vs drenaje convencional.

INTRODUCTION: knee prosthetic surgery can be associated with significant blood loss that can account for up to 20% of blood volume. The objective of our study is to analyze blood loss (BL) after total knee replacement (TKR), with the use of a blood recovery system vs a normal drain. MATERIAL AND METHODS: prospective, comparative, and observational study of two groups of 30 patients who underwent TKR, one control (CG) and another study group with a recovery system (RG). We analyzed PS, hemoglobin (Hb), hematocrit (Htc), systolic blood pressure (SBP) and diastolic blood pressure (DBP) and heart rate (HR) at 3-, 24-, 48-, 72- and 96-hours post-surgery, the need for transfusion, and the percentage of discharges in 72 hours and complications. RESULTS: the highest percentage of change in Htc and Hb occurred in the first 3 hours post-surgery and recovery began at 72 hours in the RG (p = 0.02) and at 96 hours in the CG (p = 0.04). The decrease in Hb and Htc began his recovery at 72 hours in the RG and at 96 hours in the CG. The TAS, TAD and FC began their recovery at 72 hours in both groups. The decrease in SBP was greater in the CG at 3 hours (p = 0.02), 24 hours (p = 0.02) and 48 hours (p = 0.01) post-surgery. Six patients were transfused in RG and 10 in CG (p = 0.22). 20% and 74% of the patients were discharged at 72 hours in the CG and RG, respectively. CONCLUSION: the greatest BL occurs in the first 3 hours post-surgery and recovery begins at 72-96 hours. Recovery blood system decreases BL during the first 3 hours, enhance the recuperation of Hb and SBP, decreases the need for transfusion and favors early discharge.

INTRODUCCIÓN: la cirugía protésica total de rodilla (PTR) se puede asociar a pérdidas sanguíneas (PS) significativas. El objetivo es analizar la evolución de la PS tras PTR con recuperador sanguíneo vs drenaje convencional. MATERIAL Y MÉTODOS: estudio prospectivo de dos grupos de 30 pacientes intervenidos de PTR, uno control (GC) y otro estudio con recuperador (GR). Se analizó la PS, hematocrito (Hcto), hemoglobina (Hb), tensión arterial sistólica (TAS) y diastólica (TAD) y frecuencia cardíaca (FC) a las tres, 24, 48, 72 y 96 horas postquirúrgicas, la necesidad de transfusión, el porcentaje de altas en 72 horas y las complicaciones. RESULTADOS: la mayor PS y porcentaje de cambio de Hcto y Hb se produjo a las tres horas postquirúrgicas e inició su recuperación a las 72 horas en el GR (Hcto, p = 0.02) (Hb, p = 0.04) y a las 96 horas en el GC. La TAS, TAD y FC empezó su recuperación a las 72 horas en ambos grupos. El descenso de TAS fue mayor en el GC a las tres horas (p = 0.02), 24 horas (p = 0.02) y 48 horas (p = 0.01) postquirúrgicas. Veinte y 33% de los pacientes fueron transfundidos, además 20 y 74% fueron dados de alta a las 72 horas en el GC y GR, respectivamente. CONCLUSIÓN: la mayor PS y porcentaje de cambio de Hcto y Hb se produce a las tres horas postquirúrgicas y empieza su recuperación a las 72-96 horas. El recuperador favorece la recuperación del Hcto, Hb y TAS, disminuye la necesidad de transfusión y favorece el alta precoz.

Arthrotomy debridement of arthrostic septic arthritis of the knee is more effective than arthroscopic debridement and delays the need for prosthesis despite progression. / El desbridamiento por artrotomía de la artritis séptica de rodilla artrósica es más eficaz que el artroscópico y retrasa la necesidad de prótesis a pesar de la progresión de la artrosis.

BACKGROUND AND OBJECTIVE: 40%-50% of this septic arthritis occurs in the knee, despite rapid medical surgical treatment, 24%-50% will have a poor clinical outcome. It is not clear which debridement technique, by arthrotomy or arthroscopy, is more effective in controlling infection, or whether or not previous osteoarthritis worsens the outcome. The objective of this study on septic arthritis of the osteoarthritic knee was to analyse which surgical debridement technique, arthroscopy or arthrotomy, is more effective, the clinical and radiographic outcomes of the patients, and how many go on to require a TKR after the infection has healed. MATERIAL AND METHODS: A retrospective study was performed in 27 patients with native septic arthritis of the knee. Eighteen were men and the mean age was 64.8 years (30-89years). Fifteen patients were debrided by arthrotomy and 12 by arthroscopy. The effectiveness of debridement in controlling infection, the radiographic progression of the osteoarthritis on the Ahlbäch scale, the need for subsequent replacement, and pain and functional status were analysed using the VAS and WOMAC scales at 52.8±11.2-month follow-up. RESULTS: The infection was controlled in 93% and 92% of the patients, 13% and 42% required 2 or more surgeries for infection control, 18% and 44.4% showed progression of arthritis in the arthrotomy and arthroscopy groups, respectively. One patient in each group required a knee replacement. The VAS score was superior in the arthrotomy group and there were no differences in WOMAC score. CONCLUSION: Debridement by arthrotomy in the emergency department by non-sub-specialist knee surgeons is more effective than arthroscopic debridement in controlling septic arthritis of the knee. Surgical debridement of septic arthritis in knees with previous osteoarthritis enabled control of the infection with no pain despite the progression of the osteoarthritis.

Validity of the KLIC and CRIME80 scores in predicting failure in late acute infection treated by debridement and implant retention. / Validez de las escalas KLIC y CRIME80 en la predicción del fracaso en la infección aguda tardía tratada mediante desbridamiento y retención de implantes.

It is very important to treat prosthetic infections correctly in order to ensure a higher success rate. Debridement with implant retention (DAIR) is widely used in acute and late infections, however patients who fail after this surgery are known to have a higher risk of failure in subsequent surgeries. Therefore, it is important to find a scale that enables us to predict the risk of DAIR failure. Hence the KLIC and CRIME80 scores for acute and late acute infections, respectively. This study analysed the validity of both scores in acute late periprosthetic knee infections. We observed that the KLIC score has no predictive value for this type of infection, but the CRIME80 score does.

Prognosis of venous thromboembolism in orthopaedic surgery or trauma patients and use of thromboprophylaxis. / Pronóstico de la enfermedad tromboembólica venosa en cirugía ortopédica o pacientes traumatológicos y uso de tromboprofilaxis.

BACKGROUND: There is scarce evidence about the prognosis of venous thromboembolism in patients undergoing orthopedic surgery and in patients suffering non-surgical trauma. METHODS: We used the RIETE database (Registro Informatizado de pacientes con Enfermedad Trombo Embólica) to compare the prognosis of venous thromboembolism and the use of thromboprophylaxis in patients undergoing different orthopedic procedures and in trauma patients not requiring surgery. RESULTS: From March 2001 to March 2015, a total of 61,789 patients were enrolled in RIETE database. Of these, 943 (1.52%) developed venous thromboembolism after elective arthroplasty, 445 (0.72%) after hip fracture, 1,045 (1.69%) after non-major orthopedic surgery and 2,136 (3.46%) after non-surgical trauma. Overall, 2,283 patients (50%) initially presented with pulmonary embolism. Within the first 90 days of therapy, 30 patients (0.66%; 95% CI 0.45-0.93) died from pulmonary embolism. The rate of fatal pulmonary embolism was significantly higher after hip fracture surgery (n = 9 [2.02%]) than after elective arthroplasty (n = 5 [0.53%]), non-major orthopedic surgery (n = 5 [0.48%]) or non surgical trauma (n = 11 [0.48%]). Thromboprophylaxis was more commonly used for hip fracture (93%) or elective arthroplasty (94%) than for non-major orthopedic surgery (71%) or non-surgical trauma (32%). Major bleeding was significantly higher after hip fracture surgery (4%) than that observed after elective arthroplasty (1.6%), non-major orthopedic surgery (1.5%) or non-surgical trauma (1.4%). CONCLUSIONS: Thromboprophylaxis was less frequently used in lower risk procedures despite the absolute number of fatal pulmonary embolism after non-major orthopedic surgery or non-surgical trauma, exceeded that observed after high risk procedures.

[Septic arthritis of the knee by Staphylococcus warneri]. / Artritis séptica de rodilla por Staphylococcus warneri.

Septic arthritis usually occurs as an acute joint process that can cause a rapid destruction of the cartilage, if the necessary therapeutic measures were not taken. Rarely, Staphylococcus warneri may be the cause of this pathology although due to its diagnostic difficulty we can make mistakes in its treatment. We present the case of a patient with septic arthritis of the knee by this germ and we intend to remark what are the diagnostic measures and recommendations to consider for this osteoarticular infection.

La artritis séptica suele presentarse como un proceso articular agudo que puede provocar una rápida destrucción del cartílago, si no se toman las medidas terapéuticas necesarias. De manera poco frecuente, el Staphylococcus warneri puede ser la causa de esta patología aunque por su dificultad diagnóstica podemos cometer errores en su tratamiento. Presentamos el caso de un paciente con artritis séptica de rodilla por este germen y pretendemos remarcar cuáles son las medidas diagnósticas y recomendaciones a tener en cuenta para esta infección osteoarticular.

Synthesis of a heterogeneous artificial metallolipase with chimeric catalytic activity.

A solid-phase strategy using lipase as a biomolecular scaffold to produce a large amount of Cu(2+)-metalloenzyme is proposed here. The application of this protocol on different 3D cavities of the enzyme allows creating a heterogeneous artificial metallolipase showing chimeric catalytic activity. The artificial catalyst was assessed in Diels-Alder cycloaddition reactions and cascade reactions showing excellent catalytic properties.

[The geometry of the keel determines the behaviour of the tibial tray against torsional forces in total knee replacement]. / La geometría de la quilla condiciona el comportamiento de la bandeja tibial frente a fuerzas de torsión en prótesis totales de rodilla.

The keel design of the tibial tray is essential for the transmission of the majority of the forces to the peripheral bone structures, which have better mechanical proprieties, thus reducing the risk of loosening. The aim of the present study was to compare the behaviour of different tibial tray designs submitted to torsional forces. Four different tibial components were modelled. The 3-D reconstruction was made using the Mimics software. The solid elements were generated by SolidWorks. The finite elements study was done by Unigraphics. A torsional force of 6 Nm. applied to the lateral aspects of each tibial tray was simulated. The GENUTECH® tibial tray, with peripheral trabecular bone support, showed a lower displacement and less transmitted tensions under torsional forces. The results suggest that a tibial tray with more peripheral support behaves mechanically better than the other studied designs.

Pneumococcal phosphoglycerate kinase interacts with plasminogen and its tissue activator.

Streptococcus pneumoniae is not only a commensal of the nasopharyngeal epithelium, but may also cause life-threatening diseases. Immune-electron microscopy studies revealed that the bacterial glycolytic enzyme, phosphoglycerate kinase (PGK), is localised on the pneumococcal surface of both capsulated and non-capsulated strains and colocalises with plasminogen. Since pneumococci may concentrate host plasminogen (PLG) together with its activators on the bacterial cell surface to facilitate the formation of plasmin, the involvement of PGK in this process was studied. Specific binding of human or murine PLG to strain-independent PGK was documented, and surface plasmon resonance analyses indicated a high affinity interaction with the kringle domains 1-4 of PLG. Crystal structure determination of pneumococcal PGK together with peptide array analysis revealed localisation of PLG-binding site in the N-terminal region and provided structural motifs for the interaction with PLG. Based on structural analysis data, a potential interaction of PGK with tissue plasminogen activator (tPA) was proposed and experimentally confirmed by binding studies, plasmin activity assays and thrombus degradation analyses.

[Ischial osteomyelitis in children. Two case reports]. / Osteomielitis del isquion en la infancia. A propósito de dos casos.

UNLABELLED: Ischial osteomyelitis is a bone infection that is very infrequent during childhood and is diagnosed by excluding other more frequent conditions. The definitive diagnosis is made with puncture biopsy, which allows instituting targeted antibiotic therapy. We present herein two clinical cases of two children who had a favorable course. In both cases the findings of the initial X-rays were unremarkable. The physical exam did not show total limitation of the coxofemoral joint but it did show ischial tenderness. The MRI showed images compatible with ischial osteitis. The ischial puncture biopsy was diagnostic in both cases. At the 24-month follow-up both children are leading a normal life. CONCLUSIONS: Ischial osteomyelitis is an entity to consider in children with coxalgia once other more frequent conditions have been ruled out. The diagnosis is possible with a thorough iconographic study toget.

Pneumococcal surface proteins: when the whole is greater than the sum of its parts.

Surface-exposed proteins of pathogenic bacteria are considered as potential virulence factors through their direct contribution to host-pathogen interactions. Four families of surface proteins decorate the cell surface of the human pathogen Streptococcus pneumoniae. Besides lipoproteins and LPXTG proteins, also present in other gram-positive bacteria, the pneumococcus presents the choline-binding protein (CBP) family and the non-classical surface proteins (NCSPs). The CBPs present specific structural features that allow their anchorage to the cell envelope through non-covalent interaction with choline residues of lipoteichoic acid and teichoic acid. NCSP is an umbrella term for less characterized proteins displaying moonlighting functions on the pneumococcal surface that lack a leader peptide and membrane-anchor motif. Considering the unceasing evolution of microbial species under the selective pressure of antibiotic use, detailed understanding of the interaction between pathogen and the host cells is required for the development of novel therapeutic strategies to combat pneumococcal infections. This article reviews recent progress in the investigation of the three-dimensional structures of surface-exposed pneumococcal proteins. The modular nature of some of them produces a great versatility and sophistication of the virulence functions that, in most cases, cannot be deduced by the structural analysis of the isolated modules.

Role of a cluster of hydrophobic residues near the FAD cofactor in Anabaena PCC 7119 ferredoxin-NADP+ reductase for optimal complex formation and electron transfer to ferredoxin.

In the ferredoxin-NADP(+) reductase (FNR)/ferredoxin (Fd) system, an aromatic amino acid residue on the surface of Anabaena Fd, Phe-65, has been shown to be essential for the electron transfer (ET) reaction. We have investigated further the role of hydrophobic interactions in complex stabilization and ET between these proteins by replacing three hydrophobic residues, Leu-76, Leu-78, and Val-136, situated on the FNR surface in the vicinity of its FAD cofactor. Whereas neither the ability of FNR to accept electrons from NADPH nor its structure appears to be affected by the introduced mutations, different behaviors with Fd are observed. Thus, the ET interaction with Fd is almost completely lost upon introduction of negatively charged side chains. In contrast, only subtle changes are observed upon conservative replacement. Introduction of Ser residues produces relatively sizable alterations of the FAD redox potential, which can explain the modified behavior of these mutants. The introduction of bulky aromatic side chains appears to produce rearrangements of the side chains at the FNR/Fd interaction surface. Thus, subtle changes in the hydrophobic patch influence the rates of ET to and from Fd by altering the binding constants and the FAD redox potentials, indicating that these residues are especially important in the binding and orientation of Fd for efficient ET. These results are consistent with the structure reported for the Anabaena FNR.Fd complex.

The crystal structure of tetrameric methionine adenosyltransferase from rat liver reveals the methionine-binding site.

Most of the transmethylation reactions use the same methyl donor, S-adenosylmethionine (SAM), that is synthesised from methionine and ATP by methionine adenosyltransferase (MAT). In mammals, two MAT enzymes have been detected, one ubiquitous and another liver specific. The liver enzyme exists in two oligomeric forms, a tetramer (MAT I) and a dimer (MAT III), MAT I being the one that shows a higher level of affinity for methionine but a lower SAM synthesis capacity. We have solved the crystal structure of rat liver MAT I at 2.7 A resolution, complexed with a methionine analogue: l-2-amino-4-methoxy-cis-but-3-enoic acid (l-cisAMB). The enzyme consists of four identical subunits arranged in two tight dimers that are related by crystallographic 2-fold symmetry. The crystal structure shows the positions of the relevant cysteine residues in the chain, and that Cys35 and Cys61 are perfectly oriented for forming a disulphide link. This result leads us to propose a hypothesis to explain the control of MAT I/III exchange and hence, the effects observed on activity. We have identified the methionine-binding site into the active-site cavity, for the first time. The l-cisAMB inhibitor is stacked against Phe251 aromatic ring in a rather planar conformation, and its carboxylate group coordinates a Mg(2+), which, in turn, is linked to Asp180. The essential role of the involved residues in MAT activity has been confirmed by site-directed mutagenesis. Phe251 is exposed to solvent and is located in the beginning of the flexible loop Phe251-Ala260 that is connecting the N-terminal domain to the central domain. We postulate that a conformational change may take place during the enzymatic reaction and this is possibly the reason of the unusual two-step mechanism involving tripolyphosphate hydrolysis. Other important mechanistic implications are discussed on the light of the results. Moreover, the critical role that certain residues identified in this study may have in methionine recognition opens further possibilities for rational drug design.

Directed evolution of beta -glucosidase A from Paenibacillus polymyxa to thermal resistance.

The beta-glucosidase encoded by the bglA gene from Paenibacillus polymyxa has a half-life time of 15 min at 35 degrees C and no detectable activity at 55 degrees C. We have isolated random mutations that enhance the thermoresistance of the enzyme. Following a directed evolution strategy, we have combined some of the isolated mutations to obtain a beta-glucosidase with a half-life of 12 min at 65 degrees C, in the range of resistance of thermophilic enzymes. No significant alteration of the kinetic parameters of the enzyme was observed. One of the mutants isolated in the screening for thermoresistant beta-glucosidase had the same resistance to denaturation as the wild type. This mutation caused the accumulation of enzyme in E. coli, probably due to its lower turnover. The structural changes responsible for the properties of the mutant enzymes have been analyzed. The putative causes increasing thermoresistance are as follows: the formation of an extra salt bridge, the replacement of an Asn residue exposed to the solvent, stabilization of the hydrophobic core, and stabilization of the quaternary structure of the protein.

Structural basis of the catalytic role of Glu301 in Anabaena PCC 7119 ferredoxin-NADP+ reductase revealed by x-ray crystallography.

The three-dimensional crystal structure of the Glu301Ala site-directed mutant of ferredoxin-NADP+ reductase from Anabaena PCC 7119 has been determined at 1.8A resolution by x-ray diffraction. The overall folding of the Glu301Ala FNR mutant shows no significant differences with respect to that of the wild-type enzyme. However, interesting conformational changes are detected in the side chain of another glutamate residue, Glu139, which now points towards the FAD cofactor in the active center cavity. The new conformation of the Glu139 side chain is stabilized by a network of five hydrogen bonds to several water molecules, which seem to hold the carboxylate side chain in a rather fixed position. This interacting network connects the Glu139 side chain to the Ser80 side chain through a series of three water molecules. These observations are discussed in terms of the reactivity of Glu301Ala ferredoxin-NADP+ reductase towards its substrates, and the role of Glu301 in the catalysis is re-examined. Moreover, a structural explanation of the different reoxidation properties of this mutant is given on the basis of the reported structure by modeling the hypothetical flavin C(4a)-hydroperoxide intermediate. The model shows that the distal oxygen of the peroxide anion could be in an appropriate situation to act as the proton donor in the reoxidation process.

Structural basis of increased resistance to thermal denaturation induced by single amino acid substitution in the sequence of beta-glucosidase A from Bacillus polymyxa.

The increasing development of the biotechnology industry demands the design of enzymes suitable to be used in conditions that often require broad resistance against adverse conditions. beta-glucosidase A from Bacillus polymyxa is an interesting model for studies of protein engineering. This is a well-characterized enzyme, belonging to glycosyl hydrolase family 1. Its natural substrate is cellobiose, but is also active against various artificial substrates. In its native state has an octameric structure. Its subunit conserves the general (alpha/beta)8 barrel topology of its family, with the active site being in a cavity defined along the axis of the barrel. Using random-mutagenesis, we have identified several mutations enhancing its stability and it was found that one them, the E96K substitution, involved structural changes. The crystal structure of this mutant has been determined by X-ray diffraction and compared with the native structure. The only difference founded between both structures is a new ion pair linking Lys96 introduced at the N-terminus of helix alpha2, to Asp28, located in one of the loops surrounding the active-site cavity. The new ion pair binds two segments of the chain that are distant in sequence and, therefore, this favorable interaction must exert a determinant influence in stabilizing the tertiary structure. Furthermore, analysis of the crystallographic isotropic temperature factors reveals that, as a direct consequence of the introduced ion pair, an unexpected decreased mobility of secondary structure units of the barrel which are proximal to the site of mutation is observed. However, this effect is observed only in the surrounding of one of the partners forming the salt bridge and not around the other. These results show that far-reaching effects can be achieved by a single amino acid replacement within the protein structure. Consequently, the identification and combination of a few single substitutions affecting stability may be sufficient to obtain a highly resistant enzyme, suitable to be used under extreme conditions.

Crystal structure of beta-glucosidase A from Bacillus polymyxa: insights into the catalytic activity in family 1 glycosyl hydrolases.

Family 1 glycosyl hydrolases are a very relevant group of enzymes because of the diversity of biological roles in which they are involved, and their generalized occurrence in all sorts of living organisms. The biological plasticity of these enzymes is a consequence of the variety of beta-glycosidic substrates that they can hydrolyze: disaccharides such as cellobiose and lactose, phosphorylated disaccharides, cyanogenic glycosides, etc. The crystal structure of BglA, a member of the family, has been determined in the native state and complexed with gluconate ligand, at 2.4 A and 2.3 A resolution, respectively. The subunits of the octameric enzyme display the (alpha/beta)8 barrel structural fold previously reported for other family 1 enzymes. However, significant structural differences have been encountered in the loops surrounding the active-center cavity. These differences make a wide and extended cavity in BglA, which seems to be able to accommodate substrates longer than cellobiose, its natural substrate. Furthermore, a third sub-site is encountered, which might have some connection with the transglycosylating activity associated to this enzyme and its certain activity against beta-1,4 oligosaccharides composed of more than two units of glucose. The particular geometry of the cavity which contains the active center of BglA must therefore account for both, hydrolytic and transglycosylating activities. A potent and well known inhibitor of different glycosidases, D-glucono-1,5-lactone, was used in an attempt to define interactions of the substrate with specific protein residues. Although the lactone has transformed into gluconate under crystallizing conditions, the open species still binds the enzyme, the conformation of its chain mimicking the true inhibitor. From the analysis of the enzyme-ligand hydrogen bonding interactions, a detailed picture of the active center can be drawn, for a family 1 enzyme. In this way, Gln20, His121, Tyr296, Glu405 and Trp406 are identified as determinant residues in the recognition of the substrate. In particular, two bidentate hydrogen bonds made by Gln20 and Glu405, could conform the structural explanation for the ability of most members of the family for displaying both, glucosidase and galactosidase activity.

Enantiomerically Pure alpha-Alkylidene beta-Amino Esters from Asymmetric Addition of Metal Dienolates to N-Sulfinylimines.

Lithium dienolate of 3-butenoic methyl ester was reacted with enantiomerically pure N-arylsulfinyl phenylimines (1 and 2) under different conditions. The reactions were completely regioselective-the C-C coupling occurs at the 2-position of dienolate-and highly stereoselective at the iminic carbon. In the presence of different Lewis acids (ZnCl(2), ZnBr(2), and ScTf(3)) mixtures of two alpha-vinyl, beta-arylsulfinylamino esters (epimers at C-alpha) were obtained, being the stereoselectivity depending on the nature of the aryl sulfinyl moiety and the Lewis acid used. Desulfinylation of these mixtures followed by isomerization of the double bond with Na(2)CO(3) allowed the synthesis of the optically pure (E)-alpha-ethylidene-beta-amino ester 10 in quite high overall yield. The addition of the lithium dienolate to sulfinylimines in the absence of the Lewis catalysts yielded mixtures containing important amounts of the optically pure N-arylsulfinyl alpha-ethylidene-beta-amino esters, which became the exclusive product of the reaction when N-2-methoxynaphthylsulfinyl phenylimine 2 was used as starting product.

Bone growth after periosteal stripping in rats.

The effect on bone growth after stripping of the periosteum of the middle third of the femur was investigated in 70 rats. Seventy further animals were used as controls. The animals were serially killed at 1, 2, 4, 8, 12, 16 and 20 weeks after operation. The femoral length, intertrochanteric diameter, diameter of the distal epiphysis of the femur, diameter of the femoral diaphysis and the tibial length were measured. Significant lengthening of the femur was noted only after 4 weeks, when it was 1.5% longer than the opposite side (p 0.001), but this was not maintained. The diameter of the distal epiphysis and the tibial length were not significantly affected. The intertrochanteric diameter was significantly shorter on the stripped side at the 2nd week and significantly longer at the 12th. The diaphyseal diameter of the stripped bones was progressively more narrow than the contralateral from the 2nd week. Differences remained significant at all stages of this study. Periosteal stripping yields only a temporary slight increase in bone length with a definite decrease in diaphyseal diameter.