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PubMed2005

Emergent stabilization of pelvic ring injuries by controlled circumferential compression: a clinical trial.

BACKGROUND: Pelvic ring injuries are associated with a high incidence of mortality mainly due to retroperitoneal hemorrhage. Early stabilization is an integral part of hemorrhage control. Temporary stabilization can be provided by a pelvic sheet, sling, or an inflatable garment. However, these devices lack control of the applied circumferential compression. We evaluated a pelvic circumferential compression device (PCCD), which allows for force-controlled circumferential compression. In a prospective clinical trial, we documented how this device can provide effective reduction of open-book type pelvic injuries without causing overcompression of lateral compression type injuries. METHODS: Sixteen patients with pelvic ring injuries were enrolled. Pelvic fractures were temporarily stabilized with a PCCD until definitive stabilization was provided. Anteroposterior pelvic radiographs were obtained before and after PCCD application, and after definitive stabilization. These radiographs were analyzed to quantify pelvic reduction due to the PCCD in comparison to the quality of reduction after definitive stabilization. Results were stratified into external rotation and internal rotation fracture patterns. RESULTS: In the external rotation group, the PCCD significantly reduced the pelvic width by 9.9 +/- 6.0%. This reduction closely approximated the 10.0 +/- 4.1% reduction in pelvic width achieved by definitive stabilization. In the internal rotation group, the PCCD did not cause significant overcompression. No complications were observed. CONCLUSIONS: A PCCD can effectively reduce pelvic ring injuries. It poses a minimal risk for overcompression and complications as compared with reduction alternatives that do not provide a feedback on the applied reduction force.

Adolescent↗
PubMed2005

Posterior cervical lateral mass fixation for the management of insufficient anterior stabilization.

PURPOSE: There are clinical situations when anterior fixation alone is not sufficient to adequately stabilize the cervical spine at the level of operation. In vitro biomechanical studies revealed the substantial role of posterior stabilization in such situations. However, no clinical studies of this problem have been published. The usefulness of posterior cervical lateral mass fixation when anterior stabilization failed to offer sufficient spine stability was assessed in the present study. MATERIAL AND METHODS: We enrolled 15 patients who underwent additional posterior fixation due to destabilization of the anterior one. There were five patients with rheumatoid arthritis, six with cervical discopathy, three with cervical trauma, and one with spine tumor. Improvement after posterior fixation was noted in all but one patient. RESULTS: Posterior cervical lateral mass fixation significantly improved cervical spine stability in cases with insufficiency of anterior stabilization. Further investigations on criteria helpful to predict insufficiency of anterior stabilization in cases of multisegmental cervical spine disease are needed.

Adult↗
PubMed1991

The role of fixation and bone quality on the mechanical stability of tibial knee components.

Tibial component loosening remains one of the major causes of failure of cemented and noncemented total knee arthroplasties. In this study, the authors identified the role of implant design, method of fixation, and bone density as it related to implant stability. The physical properties of "good" and "bad" bone were simulated using a "good" and "bad" foam model of the proximal tibia, fabricated in the laboratory from DARO RF-100 foam. A generic tibial component permitting various fixation designs was implanted into "good" and "bad" variable density foam tibial models in both cemented and noncemented modes. The mechanical stability of the implants was determined using a Materials Testing Machine by the application of an eccentrically applied cyclic load. The micromotion (subsidence and lift-off) of the tibial implants was recorded using two Linear Variable Differential Transformers. Statistically significant differences in implant stability were recorded as a function of fixation method. The most rigid implant fixation was achieved using four peripherally placed, 6.5-mm cancellous screws. The addition of a central stem added stability only in the case of "poor" quality foam. The mechanical stability of noncemented implants related directly to the density of the foam. Implant stability was greatly enhanced in "poor" quality foam by the use of cement. The method of implant fixation and bone density are critical determinants to tibial implant stability.

Biomechanical Phenomena↗
PubMed1990

The role of physical forces on cytotoxic T cell-target cell conjugate stability.

Theoretical considerations suggest that external forces play a significant role in cell-cell conjugate formation and may lead to the misinterpretation of adhesion data. To test this, the stability of conjugates formed between CTL and fibroblast target cells (TC) was examined in the controlled shear environment of a parallel plate flow chamber. Murine fibroblast targets expressing class I maternally transmitted Ag Mtaa or Mtab were grown on a glass slide that formed one wall of the flow chamber and were used in conjunction with anti-Mtaa and anti-Mtab specific mouse CTL clones to establish a panel of Ag-reciprocal targets and lymphocytes. Although cytolysis assays indicated that lymphocytes recognized and destroyed appropriate but not inappropriate targets, the stability of some CTL/TC conjugates was Ag independent. In all cases, the conjugate stability was shear dependent over a 100-fold range (0.04 to 4.0 dynes/cm2). For some clones, the ratio of the stabilities of Ag-specific CTL/TC conjugates to nonspecific conjugates was significantly enhanced with increasing shear. This implies that the role of Ag specificity in CTL/TC adhesion may be misinterpreted if the shear environment of CTL/TC conjugates is unknown or uncontrolled. Kinetic analysis revealed that conjugate stability was dependent on the exposure time to external forces and that there existed two populations of conjugates; weak associations that disengaged within the first 30 s of flow, and strong associations that remained attached even after a 5-min exposure to a steady shear stress. The stability of Ag-specific CTL/TC conjugates at 0.04 dynes/cm2 was enhanced by 50% as the temperature was increased from 25 to 37 degrees C, whereas the stability of nonspecific CTL/TC associations was not affected. This result indicates that significant Ag-specific strengthening may occur at physiologic temperatures. This work suggests the importance of attention to role of fluid mechanical shear stress in standard adhesion assays.

Animals↗
PubMed1986

Hepatic Ah receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin. Partial stabilization by molybdate.

In structure and general mode of action, the Ah receptor is very similar to the receptors for steroid hormones. Molybdate previously has been shown to be highly effective at preserving ligand-binding function in steroid receptors during their exposure to elevated temperature or high ionic strength and at stabilizing steroid receptors as high molecular weight oligomeric complexes. Since such stabilization by molybdate can be very useful during characterization and purification of receptors, we tested the effects of molybdate on the Ah receptor to determine if the Ah receptor, like the receptors for steroid hormones, might be stabilized. In hepatic cytosols from C57BL/6N mice and Sprague-Dawley rats, molybdate concentrations up to 30 mM in homogenizing and analysis buffers did not alter the concentration of specific Ah receptor sites detected by binding of [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin. However, inclusion of 20 mM molybdate in the homogenizing buffer did significantly protect unliganded Ah receptor from thermal inactivation at 20 degrees C and from KCl-induced loss of ligand-binding ability. In accord with previous reports, 20 mM molybdate in homogenizing and analysis buffers greatly increased the concentration of detectable glucocorticoid receptor in rat hepatic cytosol and estrogen receptor in rat uterine cytosol. Exposure to 0.4 M KC1 caused the glucocorticoid receptor from rat liver to shift sedimentation from approximately equal to 8 S to approximately equal to 4 S and caused a severe loss of specific glucocorticoid binding. Presence of 20 mM molybdate stabilized the glucocorticoid receptor as a single discrete peak sedimenting at approximately equal to 8 S. In contrast, the Ah receptor from rat liver exposed to 0.4 M KC1 in the presence of molybdate sedimented as biphasic peaks; one peak (approximately equal to 9.5 S) corresponded to the form of Ah receptor observed at low ionic strength, while the other peak (approximately equal to 5.5 S) corresponded to the form of Ah receptor seen in cytosol treated with 0.4 M KC1 in the absence of molybdate. Addition of heparin to hepatic cytosols from mice or rats shifted sedimentation of Ah receptor from approximately equal to 9.5 S to approximately equal to 5.5 S. Molybdate, again, provided stabilization in the approximately equal to 9.5 S form, but only for about one-half the total Ah receptor content in both rat and mouse hepatic cytosols. In sum, molybdate is far less effective at stabilizing rodent Ah receptors than it is at stabilizing steroid receptors in the same species.

Animals↗
PubMed1987

The role of cruciate ligaments in maintaining knee joint stability.

The role of the cruciate ligaments in maintaining the stability of the knee joint is delineated by experimental studies on 21 fresh adult knee specimens in addition to the analysis of symptoms in 111 cases of cruciate ligament injuries. Cruciate ligaments maintain not only the anteroposterior stability, but also rotational and one-plane medial or lateral stability together with the medial and lateral structures. The anterior cruciate ligament (ACL) plays a part in maintaining anterior one-plane stability and rotational stability of the knee, while the posterior cruciate ligament plays a major part in maintaining both posterior one-plane stability and rotational stability of the knee. An isolated medial (or lateral) ligament (ML) tear can only result in medial or lateral one-plane instability and an increased rotation, but no shift of the axis of rotation occurs. It is not a genuine rotational instability. Both ACL and ML tears are present in one-plane medial, one-plane anterior, and anteromedial rotational instability, but the anterior drawer test or abduction stress test may be negative if the tear of the ACL or ML is partial.

Adult↗
PubMedDate not supplied

Alveolar stability of altitude raised rats.

On the lining of alveolar membrane of the lung presence of surfactant, a surface tension lowering agent which is a phospholipid in nature, is well established. A good correlation exists between pulmonary lecithin, the principle constituent of surfactant system and alveolar stability. The production of surface active material in the type II cells is oxygen dependent and is affected by hypoxia. The chemical and physical nature of the surfactant in the lungs of the rats raised at high altitude has been studied in comparison with that of sea level control. Eighteen male adult rats raised at high altitude (3520 m) were used. Phospholipids (Phosphatidyl Choline, Phosphatidyl ethanolamine, Lysophosphatidyl choline, Lysophosphatidyl ethanolamine and Sphingomyelin) were estimated by thin layer chromatography, stability index by Pattle's bubble technique and dynamic surface tension have also been studied to assess the surfactant activity of the lung. The results indicate that there was a decrease in lung surfactant as measured by chemical analysis. However, stability ratio measurements showed that there was very little change in the stability ratio (Sr) as the value of both groups lay in the normal range namely 0.6 to 0.9 hence the lungs of high altitude raised rats had normal alveolar stability. Surface tension values of alveolar lavage in altitude raised animals were also similar to those of normal rats. It is concluded that the rats raised at altitude show a lowering of surfactant as estimated chemically but the stability ratio is not significantly altered to indicate alveolar instability. In the altitude rats lesser quantum of surfactant is adequate to maintain alveolar stability.

Altitude↗
PubMed1980

Relative resistance of the F-42-stabilized classical pathway C3 convertase to inactivation by C4-binding protein.

The sera of some patients with SLE contain an IgG antibody (F-42) directed against the classical pathway C3 convertase (C-42), which is capable of stabilizing C42 in a dose-dependent manner. The half-life (T 1/2) of C42 is prolonged by F-42. In order to determine whether C4-binding protein was capable of reversing stabilization of C42, stabilized and unstabilized cell-bound C42 were exposed to purified C4-bp and the convertase activity was assessed. C4-bp was capable of accelerating the decay of C42 in a dose-dependent manner; 2 microgram/ml C4-bp reduced the T 1/2 of C42 from 5 to 2.5 min at 30 degrees C. On the other hand, 16 microgram C4-bp could reverse stabilization of C42 by F-42 from T 1/2 = 78 min to a T 1/2 - 40 min; 128 microgram C4-bp reduced the T 1/2 of stabilized C42 to 4 min. Functional inactivation of C42 occurs via enhanced decay-dissociation of C2 from the convertase by C4-bp, as shown by the release of 125I-C2i from the cell-bound convertase. Stabilization of C42 by F-42 is caused by prevention of decay-dissociation of 125I-C2. F-42 was also capable of stabilizing C4oxy2 even further, as shown by prolongation of the T 1/2 of cell-bound C4 oxy2 to a T 1/2 of at least 300 min at 30 degrees C.

Antibodies↗
PubMed1994

Antitumor activity and pharmacokinetics in mice of a recombinant immunotoxin containing a disulfide-stabilized Fv fragment.

Disulfide-stabilized Fvs (dsFv) are recombinant Fv fragments of antibodies in which the inherently unstable VH-VL heterodimer is stabilized by a disulfide bond engineered between structurally conserved framework positions of VH and VL. We have recently described a recombinant immunotoxin, B3(dsFv)-PE38KDEL, that is composed of such a dsFv connected to a truncated form of Pseudomonas exotoxin (PE38KDEL). This disulfide-stabilized immunotoxin is indistinguishable in activity and specificity from its single-chain immunotoxin counterpart (Brinkmann et al., Proc. Natl. Acad. Sci. USA, 90: 7538-7542, 1993). We have now constructed and evaluated the stability, pharmacokinetics, and antitumor effect of a very similar disulfide-stabilized immunotoxin B3(dsFv)-PE38. This immunotoxin is specifically cytotoxic to human cancer cell lines such as A431 that express the B3 antigen on their surface. In addition, the dsFv-immunotoxin is more stable at 37 degrees C in human serum than the corresponding single-chain immunotoxin B3(Fv)-PE38. The survival of the disulfide-stabilized immunotoxin in the circulation of mice was determined by a bioassay on cultured A431 cells after administering the immunotoxin i.v. The half-life in blood was 23 min. To determine the therapeutic effects of the disulfide-stabilized immunotoxin, it was given i.v. to immunodeficient mice bearing s.c. human epidermoid carcinomas. The dsFv-immunotoxin caused complete regression of tumors with no toxic effect on mice. The antitumor effect was similar to that reported for the single-chain Fv-immunotoxin. Our data show that dsFv-immunotoxins retain full in vitro as well as in vivo activity when compared to scFv-immunotoxins. Because dsFv-immunotoxins have full activity, are more stable, and can be produced with significantly improved yields compared to scFv-immunotoxins, the dsFv-immunotoxins may be more useful for therapeutic applications than scFv-immunotoxins.

Animals↗
PubMed1993

Assessment of radiolabeled stabilized F(ab')2 fragments of monoclonal antiferritin in nude mouse model.

The biodistribution of 111In-labeled stabilized fragments of monoclonal antiferritin was studied in nude mice bearing a human hepatoma tumor xenograft. Pharmacokinetics and tumor targeting of fragment Fab'-linker-Fab' fragment molecules (stabilized F(ab')2) were compared to unmodified F(ab')2 fragment molecules and immunoglobulin G (IgG). Significant differences were observed in tumor and normal organ uptake at 12, 24, 48 and 72 hr. Tumor retention of stabilized F(ab')2 fragments was approximately 2.5-fold higher than of unmodified F(ab')2 at 48 hr. Blood clearance for stabilized F(ab')2 was relatively faster than intact IgG, while unmodified F(ab')2 cleared more rapidly from the circulation. Kidney radioactivity of unmodified F(ab')2 was at least two times higher than kidney radioactivity of stabilized F(ab')2 at all time points. Stabilized F(ab')2 demonstrated 40% less liver uptake than intact IgG. In these studies with nude mice, substantial retention of stabilized F(ab')2 in tumor and significant reduction in liver and kidney uptake of these fragments indicated that they could also have a higher therapeutic ratio than IgG or unmodified F(ab')2 in human patients.

Animals↗
PubMed1993

Visual stabilization of posture in retinitis pigmentosa and in artificially restricted visual fields.

PURPOSE: To investigate the relationship between retinitis pigmentosa (RP) progression and the visual contribution to posture stabilization; to examine the extent to which visual-field diameter affects the visual contribution to posture stabilization. METHODS: Posture information was recorded in 35 subjects with well-characterized RP and in 20 subjects with normal vision. Data were collected as each subject stood in a dark environment and as each subject viewed a stationary visual display. In both conditions, somatosensory feedback was concurrently altered. Data were also collected on 10 additional subjects with normal vision wearing field-restricting goggles (visual-field diameters ranged from 26.5 down to 6 degrees). RESULTS: RP progression is accompanied by a steady decrease of the visual stabilization of posture, from normal values at the onset of the disease to the absence of visual stabilization and, eventually, to visual destabilization of posture. Decreasing visual field diameter in the subject with normal vision resulted in a linear decrease of the visual stabilization of posture. However, subjects with RP with comparable visual-field loss showed significantly lower visual stabilization than normal subjects with artificially restricted fields. Moreover, subjects with normal vision with restricted visual fields as small as 6 degrees failed to show visual destabilization of posture. CONCLUSIONS: Most likely, the additional reduction in the visual stabilization of posture shown in subjects with RP, as well as the visual destabilizing effect manifest in the late stages of RP, is caused by anomalous processing of visual information in the remaining visual field.

Adult↗
PubMed1993

Calcium influx and protein phosphorylation mediate the metabolic stabilization of synaptic acetylcholine receptors in muscle.

During neuromuscular synapse development, the degradation rate of ACh receptors (AChRs) accumulated in the synaptic portion of the muscle membrane is drastically reduced under neural control, their half-life t1/2 increasing from 1 d to about 12 d. Recent evidence suggests that the metabolic stability of synaptic AChRs is mediated by the muscle activity induced by the nerve. We have now investigated the pathway linking muscle activity and metabolic stabilization of synaptic AChRs in organ cultured rat muscle. Soleus and diaphragm muscles were denervated for 14-40 d, a procedure leading to the destabilization of synaptic AChRs, and conditions required to restabilize synaptic AChRs in the denervated muscle were analyzed. The activity-dependent stabilization of synaptic AChRs in chronically denervated endplates required calcium entry through dihydropyridine-sensitive Ca2+ channels activated by high-frequency stimulation for approximately 6 hr and was specific for synaptic AChRs. As in vivo, extrasynaptic AChRs were not stabilized, and their t1/2 remained 1 d. The stabilization process was not dependent on de novo protein synthesis, and it could also be brought about by elevated cAMP levels. Furthermore, it required shorter stimulation periods in the presence of the phosphatase inhibitors okadaic acid and calyculin A, whereas blockade of protein kinases with high doses of staurosporine blocked the stabilization. Activity-dependent, dihydropyridine-sensitive as well as cAMP-dependent phosphorylation of myosin light chain was observed. These findings are consistent with the notion that muscle activity initiates AChR stabilization via the activation of calcium-dependent protein phosphorylation reactions.

Alkaloids↗
PubMed1993

Mechanisms of glenohumeral joint stability.

The biomechanics of glenohumeral stability involve several static and dynamic mechanisms to achieve the intricate balance between shoulder mobility and stability. In conjunction with recent in vitro studies, two important stabilizing mechanisms, concavity compression and scapulohumeral balance, were described. Concavity compression refers to the stability obtained by compressing the humeral head into the concave glenoid fossa. Increasing the magnitude of the compressive load, as provided by dynamic muscle contraction, and the depth of the glenoid concavity, which varies from the asymmetric geometry, enhance concavity compression stabilization. The related scapulohumeral balance refers to the dynamic positioning of the glenohumeral joint so that the joint reaction force is balanced within the glenoid fossa. The greater the arc provided by the glenoid, the larger the range of joint force angles acting through the humeral head that may be stabilized. The presence of an intact glenoid labrum is important to both mechanisms. Concavity compression and scapulohumeral balance may be of particular importance to glenohumeral joint stability in the midrange of motion where the capsuloligamentous constraints are lax. Clinical correlation of these mechanisms contributes to the understanding of glenohumeral instability.

Aged↗
PubMed1995

Wheelchair stability: effect of body position.

When a wheelchair user reaches and leans, the static stability decreases in the direction of the lean and increases in the opposite direction. The purpose of this study was to determine the extent of this effect. We studied 21 nondisabled subjects in a representative wheelchair, measuring the static forward, rear, and lateral stability on a tilting platform. Reaching and leaning away from the tip added stability, with mean increases ranging from 9.1% to 124.3% of the neutral-position values, whereas reaching and leaning toward the tip reduced stability, with mean decreases ranging from 25.2% to 52.3% (p < 0.0001). The stability range ("away" minus "toward") varied from 52.4% to 149.5%. Reaching forward had a greater effect on stability than did reaching back or to the side. Wheelchair users with the ability to control their body positions can profoundly affect the stability of their wheelchairs, a factor that should be considered in wheelchair selection and training.

Adult↗
PubMed1997

The comparative efficacy of stabilized stannous fluoride dentifrice, peroxide/baking soda dentifrice and essential oil mouthrinse for the prevention of gingivitis.

This double-blind parallel-design clinical study compared the efficacy of a stabilized stannous fluoride dentifrice (Crest Plus Gum Care), baking soda and peroxide (NaF) dentifrice (Mentadent), and essential oil mouthrinse (Listerine) to a conventional NaF dentifrice (Crest) for the control of plaque, gingivitis and gingival bleeding over six months. Following an initial baseline examination and stratification, subjects received a complete oral prophylaxis and were distributed assigned test products. Following three and six months, subjects re-visited the clinic for examinations. Evaluations at baseline and at 3 and 6 months included soft tissue status. Löe-Silness gingivitis/gingival bleeding, Silness-Löe plaque and dental stain. Results subsequent to six months of product use were as follows: At six months, the stabilized stannous fluoride dentifrice was observed to produce statistically significant 17.5% reductions in gingivitis and 27.5% reductions in gingival bleeding relative to the NaF dentifrice. The combination of sodium fluoride dentifrice and essential oil mouthrinse produced statistically significant reductions of 7.4% in gingivitis and 10.8% in plaque as compared with the NaF dentifrice. The stabilized stannous fluoride dentifrice produced statistically significant reductions in both gingivitis (10.8%) and gingival bleeding (23.0%) relative to the combination of sodium fluoride dentifrice and essential oil mouthrinse. The baking soda and peroxide (NaF) dentifrice did not provide reductions in gingivitis, plaque or gingival bleeding as compared with the conventional NaF dentifrice. The stabilized stannous fluoride dentifrice provided statistically significant reductions in gingivitis as compared with the baking soda and peroxide dentifrice following six months of use, and both the essential oil mouthrinse and stabilized stannous fluoride dentifrice provided statistically significant reductions in gingivitis as compared with the baking soda and peroxide dentifrice following three months of use. These results support: 1) the efficacy of stabilized stannous fluoride dentifrice and the combination of sodium fluoride dentifrice and essential oil mouthrinse for the prevention of gingivitis; 2) the superior activity of stabilized stannous fluoride dentifrice as compared with a combination of sodium fluoride dentifrice and essential oil mouthrinse for the control of gingivitis and gingival bleeding; and 3) the lack of efficacy for baking soda and peroxide dentifrice for the control of plaque, gingivitis and gingival bleeding as compared with conventional fluoridated dentifrice.

Adult↗
PubMed1998

What ultrastable globular proteins teach us about protein stabilization.

Proteins, due to their delicate balance of stabilizing and destabilizing interactions, are only marginally stable if physiological conditions are considered as the standard state. Enhanced intrinsic stability of "ultrastable" proteins, e.g., from extremophiles, requires only minute local structural changes. Thus, general strategies of stabilization are not available for temperature, pH, salt, or pressure adaptation. Mechanisms of enhanced thermal stability involve improved packing or docking of structural elements (domains, subunits), as well as specific local interactions, e.g., networks of ion pairs. Relating the structure and stability of eye lens crystallins (which do not undergo any turnover during the life time of an organism), point mutations, nicking and swapping of domains, grafting of linker peptides between domains, and denaturation-renaturation allowed the cumulative nature of protein stability and its relation to the hierarchy of protein structure and folding to be established. In this review, recent results for crystallins and enzymes from hyperthermophiles will be discussed as models to illustrate mechanisms of protein stabilization.

Hydrogen-Ion Concentration↗
PubMed1998

[Post-transcriptional regulation of gene expression in eukaryotes: effect of stressors on mRNA stability in vitro].

The effect of field drought on gene expression in developing Zea mays L. grain and the influence of the imbalance of essential amino acids on the expression of genes in white-rat liver at the mRNA stability level were studied. A special ommp system, which included incubation (65 degrees C, 5 min) of an aqueous preparation of highly purified, high molecular-weight RNA isolated in the presence of Mg2+, was used for the analysis of mRNAs relative stability in eukaryotes. Drought changed the relative stability of seven specific mRNA in the maize developing grain: there occurred a considerable stabilization of the eEF-1 alpha mRNA and, conversely, a destabilization of the 19-kDa zein mRNA. The imbalance for lysine and tryptophan reduced the stability of the total polyadenylated mRNA and the eEF-1 alpha mRNA of rat liver. The mRNA stability positively correlated with animal growth. Thus, using the ommp system, the effect of stressful factors on the stability of specific mRNA in eukaryotes--depending on mRNA species, stressful factors, and the tissue--was shown.

Animals↗
PubMed2001

Effect of sucrose/raffinose mass ratios on the stability of co-lyophilized protein during storage above the Tg.

PURPOSE: To examine the potential of raffinose as an excipient in stabilizing protein and to study the effect of sucrose/raffinose mass ratios on the stability of co-lyophilized protein and amorphous solids during storage at an elevated temperature. METHODS: Glucose-6-phosphate dehydrogenase (G6PDH) was colyophilized with sucrose and raffinose mixed at different mass ratios. The activity of dried G6PDH was monitored during storage at 44 degrees C. Thermal properties of sucrose/raffinose matrices were determined by differential scanning calorimetry (DSC). RESULTS: Mass ratios of sucrose to raffinose did not affect the recovery of G6PDH activity after freeze-drying, but significantly affected the stability of freeze-dried G6PDH during storage. The sucrose-alone formulation offered the best enzyme stabilization during storage. With increasing fraction of raffinose, the G6PDH stability decreased, sugar crystallization inhibited, and crystal-melting temperature increased. CONCLUSIONS: Despite the higher Tg of the formulations with higher fraction of raffinose, they provided less protection for G6PDH than did sucrose alone during storage. Our data do not support the prediction from recent thermophysical studies that raffinose should be superior to sucrose and trehalose as a potential excipient or stabilizer.

Drug Stability↗