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Surgical stabilization of the cervical spine. A comparative analysis of anterior and posterior spine fusions.

Two hundred twenty-two cervical spine stabilization procedures in 212 patients are reviewed. In 114 posterior cervical fusions, 88 anterior fusions, and ten combined procedures, no deaths occurred. Surgical complication rates were similar, but more severe complications were noted with anterior cervical fusions, including tracheoesophageal problems and transient neurologic loss. Six cases of graft dislodgement requiring reoperation also occurred. In long-term follow-up evaluations, 36 anterior fusion patients developed progressive kyphotic deformity averaging 22 degrees between surgery and the time solid fusion was obtained. Degenerative changes above and below the fusion mass were detected in 36 of 59 patients treated by anterior surgery. Posterior cervical fusion patients were noted to have no significant late change in alignment, and degenerative changes were infrequent. However, 73 of 98 patients had significant extension of fusion mass beyond the originally intended levels of stabilization. Because anterior cervical spine fusion was associated with significant complications of graft dislodgement and tracheoesophageal trauma, as well as postsurgical progressive deformity, the authors recommend posterior wiring and fusion as the procedure of choice to treat cervical spine instability and permit halo-free postsurgical rehabilitation. When anterior neural decompression and fusion is necessary, concomitant posterior wiring and fusion or halo vest immobilization may be necessary to maintain reduction and prevent kyphotic angulation, because posterior ligamentous disruption is not always grossly evident on radiographic examination.

Adolescent↗

Potentiometric analysis of UDP-galactopyranose mutase: stabilization of the flavosemiquinone by substrate.

UDP-galactopyranose mutase is a flavoprotein which catalyses the interconversion of UDP-galactopyranose and UDP-galactofuranose. The enzyme is of interest because it provides the activated biosynthetic precursor of galactofuranose, a key cell wall component of many bacterial pathogens. The reaction mechanism of this mutase is intriguing because the anomeric oxygen forms a glycosidic bond, which means that the reaction must proceed by a novel mechanism involving ring breakage and closure. The structure of the enzyme is known, but the mechanism, although speculated on, is not resolved. The overall reaction is electrically neutral but a crypto-redox reaction is suggested by the requirement that the flavin must adopt the reduced form for activity. Herein we report a thermodynamic analysis of the enzyme's flavin cofactor with the objective of defining the system and setting parameters for possible reaction schemes. The analysis shows that the neutral semiquinone (FADH(*)) is stabilized in the presence of substrate and the fully reduced flavin is the anionic FADH(-) rather than the neutral FADH(2). The anionic FADH(-) has the potential to act as a rapid 1-electron donor/acceptor without being slowed by a coupled proton transfer and is therefore an ideal crypto-redox cofactor.

Bacterial Proteins↗

Tension-band stabilization of transverse fractures: an experimental analysis.

Fifty-two pig metacarpal bones were osteotomized and internally fixed using a variety of wiring techniques. Fixed constructs were then loaded to failure while several biomechanical parameters were measured. Tension-band stabilization provided superior strength, stiffness, and approximation. Crossed K-wire fixation was distinctly inferior with regard to these same parameters.

Animals↗

Study on structure and characterization of inclusion complex of gossypol/beta cyclodextrin.

The inclusion complex of beta-cyclodextrin with gossypol was synthesized by using a convenient method of microwave irradiation. The structure of the complex was determined by 1H NMR, IR spectroscopy, and as well as the elemental analysis; the thermal stability was studied by means of differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The association constant between gossypol and beta-cyclodextrin measured via UV spectroscopy was 4462M(-1) at room temperature, following stoichiometry 1:2.

Carcinogens↗

Stability and motion of a hairpin and the corresponding mismatched duplex: a theoretical exploration using molecular mechanics and normal mode analysis of 2D NMR results on d(GCCGCAGC).

The oligomer d(GCCGCAGC) can adopt two different conformations: i) a duplex with two mismatched A.C base pairs and ii) a hairpin with two C.G base pairs and a single stranded loop. We report molecular mechanics, normal mode analysis, and thermodynamic stability calculations for both structures. We show that the energy-minimized structure and harmonic-dynamics results are in complete agreement with the observed NOE spectrum and imino proton exchange data. We conclude that the high stability of the hairpin structure over the duplex at low salt concentration is due to the higher vibrational entropy contribution to the system free energy by the single stranded loop and to the lack of minor groove phosphate/phosphate electrostatic repulsions that tend to destabilize the duplex.

Base Composition↗

Use of statins and breast cancer: a meta-analysis of seven randomized clinical trials and nine observational studies.

PURPOSE: A growing body of evidence suggests that statins may have chemopreventive potential against breast cancer. Laboratory studies demonstrate that statins induce apoptosis and reduce cell invasiveness in various cell lines, including breast carcinoma cells. However, the clinical relevance of these data remains unclear. The nonconclusive nature of the epidemiologic data prompted us to conduct a detailed meta-analysis of the studies published on the subject in peer-reviewed literature. PATIENTS AND METHODS: A comprehensive search for articles published up until 2005 was performed; reviews of each study were conducted; and data were abstracted. Before meta-analysis, the studies were evaluated for publication bias and heterogeneity. Pooled relative risk (RR) estimates and 95% CIs were calculated using the random and the fixed-effects models. Subgroup and sensitivity analyses were also performed. RESULTS: Seven large randomized trials and nine observational studies (five case-control and four cohort studies) contributed to the analysis. We found no evidence of publication bias or heterogeneity among the studies. Statin use did not significantly affect breast cancer risk (fixed effects model: RR = 1.03; 95% CI, 0.93 to 1.14; random effects model: RR = 1.02; 95% CI, 0.89 to 1.18). When the analyses were stratified into subgroups, there was no evidence that study design substantially influenced the estimate of effects. Furthermore, the sensitivity analysis confirmed the stability of our results. CONCLUSION: Our meta-analysis findings do not support a protective effect of statins against breast cancer. However, this conclusion is limited by the relatively short follow-up times of the studies analyzed. Further studies are required to investigate the potential decrease in breast cancer risk among long-term statin users.

Breast Neoplasms↗

Structural analysis and prediction of protein mutant stability using distance and torsion potentials: role of secondary structure and solvent accessibility.

Analyzing the factors behind protein stability is a key research topic in molecular biology, and has direct implications on protein structure prediction and protein-protein interactions. We have analyzed protein stability upon point mutations using a distance-dependant pair potential representing mainly through-space interactions, and torsion angle potential representing mainly neighboring effects as a basic statistical mechanical setup for the analysis. The synergetic effect of accessible surface area and secondary structure preferences was used as a classifier for the potentials. In addition, short-, medium-, and long-range interactions of the protein environment were also analyzed. Two datasets of point mutations were taken for the comparison of theoretically predicted stabilizing energy values with experimental DeltaDeltaG and DeltaDeltaGH(2)O from thermal and chemical denaturation experiments. These include 1538 and 1603 mutations, respectively, and contain 101 proteins that share a wide range of sequence identity. The resulting force fields were carefully evaluated with different statistical tests. Results show a maximum correlation of 0.87 with a standard error of 0.71 kcal/mol between predicted and measured DeltaDeltaG values and a prediction accuracy of 85.3% (stabilizing or destabilizing) for all mutations together. A correlation of 0.77 (more than 80% prediction accuracy with a standard error of 0.95 kcal/mol) each for the test dataset of split-sample validation and fivefold crossvalidation was obtained and a correlation of 0.70 (77.4% prediction accuracy with a standard error of 1.17 kcal/mol) was shown by the jackknife test. The same model was implemented, and the results were analyzed for mutations with DeltaDeltaGH(2)O. A correlation of 0.78 (standard error 0.96 kcal/mol) was observed with a prediction efficiency of 84.65%. This model can be used for the future prediction of protein structural stability together with various experimental techniques.

Databases, Protein↗

Production and characterization of monoclonal antibodies to the sperm acrosome stabilizing factor (ASF): utilization for purification and molecular analysis of ASF.

Utilizing hybridoma technology and highly purified acrosome stabilizing factor (ASF), six monoclonal antibodies (mAbs) specific for ASF were produced and characterized. Specificity and binding properties of each clone were examined by immunoperoxidase labeling of electrophoretic blots of rabbit serum, seminal plasma, cauda epididymal fluid and vasectomized seminal plasma separated on native and sodium dodecyl sulfate (SDS)-polyacrylamide gels. All mAbs recognize ASF in seminal plasma and cauda epididymal fluid but do not bind components in serum or vasectomized seminal plasma. Purification of ASF by affinity chromatography utilizing the mAbs, has shortened the 6-day isolation procedure for ASF used previously to less than 2 h and has increased the yield from 2 micrograms to 300 micrograms of ASF obtained per ml of seminal plasma. Three mAbs were used in conjunction with Cleveland digest with Staphylococcus aureus V8 protease, SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoperoxidase labeling of Western Blots, to identify peptides containing specific determinants recognized by each mAb. At least five separate determinants were recognized by the six mAbs. The sensitivity of the Western blotting technique in conjunction with the specificity of the mAbs was exploited to detect polymeric forms of ASF in seminal plasma and cauda epididymal fluid. ASF is shown to be a 360-kd dimer consisting of two identical 180-kd monomers. Tools are now available to develop sensitive qualitative and quantitative assays for ASF, thus providing rapid, extremely sensitive methods for evaluating experiments designed to probe the molecular mechanism of capacitation.

Acrosome↗

A pH-stability study of phoslactomycin B and analysis of the acid and base degradation products.

Phoslactomycin B (PLM-B), a potent and selective inhibitor of serine threonine phosphatase is of interest for its antitumor, antifungal and antiviral activity. Described herein is an evaluation of the solution stability of phoslactomycin B at various pH and temperature conditions. Phoslactomycin B was produced from a NPI mutant strain of Streptomyces sp. HK-803 and purified by semi-preparative HPLC. A study of PLM-B degradation was carried out in the pH range of 2 approximately 10 at 30 degrees C and 50 degrees C using an HPLC assay. The PLM-B decomposition was observed to exhibit a U-shaped pH profile and demonstrated both acid and base-catalyzed decomposition. The decomposition could be described by the equation kOBS=kH x 10(-PH) + kOH x 10(pH-14) (kH=45 +/- 7 M(-1) h (-1); kOH= 448+/-73 M(-1h)(-1). PLM-B was found to be most stable at pH 6.63. The major acid and base products were separated and purified. Mass spectroscopic and NMR analysis revealed hydrolysis of the alpha, beta-unsaturated lactone provided the major degradation product under base conditions. Two other products in which hydration of the alpha, beta-unsaturated double bond preceded hydrolysis or methanolysis of the lactone were obtained. Under acidic condition MS and NMR analysis revealed that a dehydration step provided a C9-C11 phosphorinane derivative of PLM-B as one of the major products. The remaining acid degradation products were shown to be mixture of various dehydration products containing an additional double bond in central core of the PLM-B carbon skeleton. The major acid and base degradation products had dramatically reduced antifungal activity despite retaining the same structural core.

Hydrogen-Ion Concentration↗

A comparison of data analysis methods for determining gas phase stabilities by CID: alkali metal complexes of polyether ionophore antibiotics.

The gas phase stabilities of Group I metal complexes of the polyether ionophore antibiotics lasalocid and monensin were investigated by collision induced dissociation mass spectrometry. Electrospray ionization was used with a triple quadrupole mass spectrometer for the determination of threshold dissociation energies upon application of increasing collision energies. Various data analysis techniques for the determination of dissociation energies are discussed to assess the most suitable method for determining the stabilities of the ionophore-metal complexes studied here. In all cases only the relative stabilities of different complexes may be obtained by the method presented in this study, which does not assess absolute gas phase dissociation energies. Correction factors have been applied, however, to account for the energy conversion during collisions of different metal complexes and the varying degrees of freedom of different sized ligands, allowing for the comparison of the stabilities of different ionophores with like-metals. The measured threshold dissociation energies were compared with respect to the ionic radius of the metal cation, revealing a maximum stability for the K+ complexes of both lasalocid and monensin. A striking decrease in the stabilities of the Rb+ and Cs+ complexes was observed and is believed to be related to a decreasing degree of coordination that the ionophores can accomplish with the larger metals.

Algorithms↗

Efficiency and stability of high molecular weight DNA transformation: an analysis in tomato.

The efficiency of the binary bacterial artificial chromosome (BIBAC) vector for Agrobacterium-mediated stable transfer of high molecular weight DNA into plants was tested in tomato. Several variables affecting transformation efficiency were examined including insert size, Agrobacterium genetic background, and the presence of additional copies of the virG, virE1 and virE2 genes. It was found that a helper plasmid containing extra copies of virG was an absolute requirement for obtaining tomato transformants with the BIBAC. MOG101 with the virG helper plasmid was found to be the most efficient strain for transfer of high molecular weight DNA (150 kb). Selected high molecular weight DNA transformants were advanced several generations (up to the R4) to assess T-DNA stability. This analysis showed that the T-DNA was stably maintained and inherited through several meioses regardless of whether it was in the hemizygous or homozygous state. Expression of a selectable marker gene within the T-DNA was also examined through several generations and no gene silencing was observed. Thus, the BIBAC is a useful system for transfer of large DNA fragments into the plant genome.

Base Sequence↗

Data analysis of kinetic modelling used in drug stability studies: isothermal versus nonisothermal assays.

PURPOSE: Kinetic modelling was applied to predict the stability of cholecystokinin fragment CCK-4 in aqueous solution, which was analyzed by isothermal and nonisothermal methods using a validated stability indicating HPLC method. METHODS: The isothermal studies were performed in the temperature range 40 to 80 degrees C at pH 12 and ionic strength 0.01 M as constants, whereas nonisothermal stability studies were performed using a linear increasing temperature program, heating rate 0.25 degrees C/h and a temperature interval 40-82 degrees C. The isothermal studies require two-step linear regression to estimate the parameters, resulting in a well-defined confidence interval. Nonisothermal kinetic studies require nonlinear or linear regression by previous transformation of data to estimate the parameters. In this case, the two most popular approaches, derivative and integral, were used and compared. RESULTS: Under isothermal conditions, an apparent first-order degradation process was observed at all temperatures. The linear Arrhenius plot suggested that the CCK-4 degradation mechanism was the same within the studied temperature range, with quite large uncertainties due to the small number of degrees of freedom based only on the scatter in the plot, and giving an estimated shelf life at 25 degrees C of 35.2 days. The derivative approach yields high variability in the Arrhenius parameters, since they are dependent on the number of polynomial terms chosen, so several statistical criteria were applied to select the best model. The integral approach allows activation parameters to be calculated directly from experimental data, and provides results in good agreement with those of the traditional method, but have the advantage that the uncertainty in the final result directly reflects the goodness of fit of the experimental data to the chosen kinetic model. The application of the bootstrap technique to estimating confidence limits for the Arrhenius parameters and shelf life is also illustrated, and shows there is no difference between the asymptotic and bootstrap confidence intervals. CONCLUSIONS: Nonisothermal studies give us fast and valuable information about drug stability, although their potential for predicting isothermal behaviour is conditioned by the data analysis method applied.

Drug Stability↗

Comparative analysis of the structure and thermal stability of sea urchin peristome and rat tail tendon collagen.

We have purified collagen from two distinct sources; the vertebrate, rat tail tendon and an invertebrate, sea urchin adult tissue, the peristome. The collagenous nature of the purification products was confirmed by amino acid compositional analysis. Both preparations had high contents of glycine and proline residues and hydroxyproline was also present. The total pyrrolidine (proline+hydroxyproline) content decreased from 17.9 mole% in rat tail collagen to 12.9 mole% in peristome collagen. Distinctly different circular dichroic spectra were measured for these collagens. Analyses of spectra, measured as a function of temperature, revealed distinct thermal denaturation profiles. The melting temperature for rat tail collagen was 38.5 degrees C, while the corresponding value for peristome collagen was significantly lower at 27 degrees C. A similar thermal denaturation profile was obtained for rat tail collagen in digestion experiments using a 41-kDa gelatinase activity, isolated from sea urchin eggs. These results identify structural differences between a typical, vertebrate type I fibrillar collagen and an echinoderm collagen which serves as a constituent of a mutable connective tissue. These differences may relate to the functional roles played by collagen in these distinctly different tissues.

Amino Acids↗

Biochemical stabilization enhances red blood cell recovery and stability following cryopreservation.

Glycerolized red blood cells (RBC) are approved for long-term cryopreservation. However, the need to remove the glycerol cryoprotectant prior to transfusion has limited the usefulness of this cryopreservation method. This report describes using non-cryoprotectant biochemical stabilization techniques to substitute for the standard glycerol cryoprotectant. The glycerolized RBC method was compared to a newly developed LC-V method that combines transfusable cryoprotectants (hydroxyethyl starch and dextran) and specific non-cryoprotectant biochemical stabilizers (nicotinamide, nifedipine, and flurbiprofen). Results demonstrate that the biochemical stabilizers significantly reduce cryopreservation-induced hemolysis compared to cryopreservation in their absence and that thaw hemolysis levels approach those of standard 40% (w/v) glycerolized RBC (3.1+/-0.2% for 40% glycerol compared to 8.7+/-0.9% for the LC-V protocol). Furthermore, LC-V cryopreserved RBC exhibit a significantly enhanced post-thaw stability compared to glycerolized RBC as determined by osmotic fragility index (0.557+/-0.034 for 40% glycerol compared to 0.478+/-0.016 for the LC-V protocol). Analysis of biochemically stabilized RBC proteins revealed a transient translocation of carbonic anhydrase to the membrane fraction. However, the enhanced RBC recovery and stability could not be attributed to this event. Finally, DSC analysis demonstrated that the biochemical stabilizers of the LC-V process were not functioning as surrogate cryoprotectants in that they did not affect the quantity or quality of ice formed. Overall, this work demonstrates that cryopreservation-induced RBC damage may be corrected or prevented through specific biochemical stabilization and represents a significant step toward a directly transfusable cryopreserved RBC product.

Blood Preservation↗

Role of flow shear in the ballooning stability of tokamak transport barriers.

A tokamak's confinement time is greatly increased by a transport barrier (TB), a region having a high pressure gradient and usually also a strongly sheared plasma flow. The pressure gradient in a TB can be limited by ideal magnetohydrodynamic instabilities with a high toroidal mode number n ("ballooning modes"). Previous studies in the limit n--> infinity showed that arbitrarily small (but nonzero) flow shears have a large stabilizing influence. In contrast, the more realistic finite n ballooning modes studied here are found to be insensitive to sub-Alfvénic flow shears, provided the magnetic shear s approximately 1 (typical for TBs near the plasma's edge). However, for the lower magnetic shears that are associated with internal transport barriers, significantly lower flow shears will influence ballooning mode stability, and flow shear should be retained in the analysis of their stability.

Journal Article↗

Direct analysis of an oligomeric hindered amine light stabilizer in polypropylene materials by MALDI-MS using a solid sampling technique to study its photostabilizing action.

A novel method for the direct analysis of small amounts of an oligomeric hindered amine light stabilizer (HALS) occluded in polypropylene (PP) material was developed to study its photostabilizing action on the basis of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) using a solid sampling technique while avoiding troublesome solvent extraction. In this sampling protocol, the powdered mixture of PP composite sample containing trace amounts of an oligomeric HALS, Adekastab LA-68LD (MW = 1900), and the matrix reagent (dithranol) was spotted on the sample plate, then ion exchanged water was deposited onto the mixture to make a suspension, and finally, the dried mixture adhered on the plate was subjected to MALDI-MS measurement. On the mass spectrum thus obtained by the solid sampling MALDI, the molecular ions of the HALS desorbed from the PP composite were clearly observed as three major series of the HALS components in the range up to about m/z 7000 with little interference by the PP substrate and the other additives. Moreover, in the MALDI-MS spectra for the UV-exposed sample, the satellite peaks around the major HALS components proved to enhance significantly, reflecting the oxidized HALS species at the tetramethylpiperidine units to cause the photostabilizing action. In addition, hydrolyzed HALS species were also observed for the irradiated sample. These results suggest that not only the oxidation reaction but also the hydrolysis or decomposition of the oligomeric HALS components competitively proceed in the PP composites during UV exposure.

Journal Article↗