Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “stability”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed1975

Stability of stabilized nitroglycerin tablets in typical distribution and administration systems.

A study was undertaken to determine whether or not the present extreme restrictions on the packaging of nitroglycerin tablets are indeed necessary when dispensing the newer stabilized tablets. Baseline tests were conducted on two molded and two compressed sublingual nitroglycerin tablets to determine weight variation, content uniformity, average potency and friability. Stability tests included: (1) use test designed to simulate patient use from a single bottle of 100 tablets over a one-month period; (2) an open plate study wherein tablets were exposed to the atmosphere for 100 days; (3) strip packaging of tablets using foil-foil or foil-cello systems; (4) placement of tablets in medication cups for a seven-day period; (5) repackaging 30-tablet batches in a variety of common prescription containers. All brands of tablets retained potency during normal use when dispensed and stored in their original containers. However, one brand was superior to all others when placed under stress conditions such as open plate exposure. These tablets also retained labeled potency when exposed in a medication cup for a seven-day period, or when repackaged in either foil-foil or foil-cello strips, or when dispensed in a number of ordinary prescription containers. The study indicated that this brand of nitroglycerin tablets might be handled like any other solid dosage form in hospital distribution systems without endangering patient care. However, exceptions to present packaging restrictions must be cleared with the Food and Drug Administration.

Drug Packaging↗
PubMedDate not supplied

Accelerated stability of Ibuprofen-Eudragit RSPM sustained release tablets, IR and DSC solid stability testing.

Preformulated Ibuprofen-Eudragit RSPM sustained release tablets were subjected to accelerated stability testing at 25, 37 and 45 degrees C for 6 months. The stored tablets were evaluated for the intact drug in the formula, drug-polymer interaction and compatibility of the drug with the formulated excipients using infra red spectroscopy (IR) and differential scanning calorimetry (DSC). The IR spectrum of Ibuprofen in the tablets prepared by 15% w/v Eudragit RSPM as a granulating agent and containing 23% w/v Avicel pH 102 as an excipient is similar to the IR of standard Ibuprofen. There is no change in the IR spectra of the tablet components before and after storage of those tablets at the different investigated temperatures for 1, 3 and 6 months. The DSC thermograms of the Ibuprofen stored tablets show that the drug was still in the highly pure (> 98%) crystalline form and there was no significant degradation after storage indicating the stability of the drug on storage. In detecting Ibuprofen purity in the stored tablets, plotting of the sample temperature versus the reciprocal of the fraction of Ibuprofen melted showed deviation from Van 't Hoff linear plot.

Acrylic Resins↗
PubMed1994

Method-dependent variations in the stability of apolipoprotein B in a stabilized liquid reference material.

Using accelerated Arrhenius-type short-term and long-term temporal studies, we evaluated the storage life of a stabilized, liquid-frozen reference material (SLRM) for human apolipoprotein B (apo B) developed by the International Federation of Clinical Chemistry. As measured by our candidate reference RIA, the concentrations of immunoreactive apo B in the SLRM showed pronounced degradation with exposure to increasing temperatures over time. The SLRM was stable for as long as 1 year when stored at - 70 degrees C, but its immunoreactive apo B declined by < 10% when stored at 4 degrees C for 10 months. Using radial immunodiffusion and an ELISA to assess the equivalency of measured mass for the accelerated thermal stability of the SLRM, we found a loss of immunoreactive apo B similar to that measured by RIA. Analyzing the same samples by liquid immunoprecipitation (nephelometry) resulted in the amount of apo B present being overestimated, especially in samples held for long periods. By using different immunological methods to evaluate this thermally aged SLRM, we demonstrated that its measured behavior varies depending on the method of quantitation.

Apolipoproteins B↗
PubMedDate not supplied

Storage stability of stabilized MLV and REV liposomes containing sodium methotrexate (aqueous & lyophilized).

Multilamellar and unilamellar liposomes containing sodium methotrexate (MTX) were prepared by thin film hydration and reverse-phase evaporation methods. Encapsulation efficiency and release of MTX from liposomes at 4 degrees C, 25 degrees C and 37 degrees C were determined. When stored at 25 degrees C the liposomes lost 33% MTX after one month. To stabilize liposomes, they were freeze-dried in presence of different amounts of cryoprotectants (trehalose, PEG 10,000, PEG 20,000, and a mixture of trehalose-PEG 20,000). Measurements showed that the mixture of trehalose-PEG 20,000 imparted an MTX retention of about 70% after lyophilization. Stability tests of the lyophilized product at 4 degrees C, 25 degrees C and 37 degrees C demonstrated they were fairly stable even at 37 degrees C, indicating their potential use in commercial applications.

Drug Carriers↗
PubMed1994

Stabilization of interleukin-2 receptor alpha chain mRNA by HTLV-1 Rex in mouse L cells: lower amounts of Rex do not stabilize the mRNA.

T cell growth factor receptor, interleukin-2 receptor alpha chain (IL-2R alpha) is constitutively expressed on human T-cell leukemia virus type-1 (HTLV-1) infected T cells. We have established L cell lines which express both IL-2R alpha and the Rex protein of HTLV-1. We found that IL-1R alpha mRNA is stabilized in a cell line, Ltk/1-2a, which expresses a high amount of the Rex protein. In the presence of lower amounts of Rex, stabilization of the mRNA was not observed. These results may well explain the mechanism by which most of the lymphocytes infected with HTLV-1 escape from malignant transformation.

Animals↗
PubMed1995

Mutations that stabilize folding intermediates of phage P22 tailspike protein: folding in vivo and in vitro, stability, and structural context.

The folding of the trimeric phage P22 tailspike protein is affected by single amino acid substitutions designated temperature-sensitive folding (tsf) mutations. Their phenotypes are alleviated by two repeatedly isolated global suppressor (su) mutations (su V331A and su A334V) and by two additional substitutions (su V331G and su A334I), accessible through site-directed mutagenesis. We investigated the influence of the suppressor mutations on tailspike refolding in vitro, on its maturation at high expression levels in vivo, and on the rates of thermal unfolding of the native protein. All su mutations improved the folding efficiency in vitro and in vivo, but the relative effects of substitutions at position 334 were more pronounced in vivo, whereas the 331 substitutions were more effective in vitro. V331G caused the strongest increase in refolding yields of any single mutation, and was as effective as the V331A/A334V double mutation, where the two single mutations exhibited an additive effect. Both V331A and V331G retarded thermal denaturation, while A334V did not affect, and A334I accelerated unfolding. A334I is the first mutation found to affect the folding of the tailspike and the thermal stability of the native protein in opposite directions. The observed effects can be rationalized on the basis of the recently determined crystal structure of an N-terminally shortened tailspike. As the backbone dihedral angles of Val331 (phi = -119 degrees, psi = -142 degrees) are unusual for non-glycine residues, V331G and V331A may remove steric strain and thereby stabilize folding intermediates and the native protein. The beta-branched side-chains of Val and Ile substituted for Ala334 in the interior of the protein may improve a hydrophobic stack of residues in the large parallel beta-helix. This is likely important in loosely structured early folding intermediates, but not in the very rigid native structure, where the side-chain of Ile can hardly be accommodated.

Bacteriophage P22↗
PubMed1988

Self-stabilization of neuronal networks. II. Stability conditions for synaptogenesis.

This study is concerned with synaptic reorganization in local neuronal networks. Within networks of 30 neurons, an initial disequilibrium in connectivity has to be compensated by reorganization of synapses. Such plasticity is not a genetically determined process, but depends on results of neuronal interaction. Neurobiological experiments have lead to a model of the behavior of individual neurons during neuroplastic reorganization, formalized as a "synaptogenetic rule" that governs changes in the amount of synaptic elements on each neuron. When this synaptogenetic rule is applied to a system of neurons, there is some freedom left to the choice of further conditions. In this study it is examined, which assumptions additional to the synaptogenetic rule are essential in order to obtain morphogenetic stability. By explicating these assumptions, their plausibility can be tested. It is analysed, in which respect these conditions are important, in which part of the model they exert their influence, and what kind of instability and degeneration happens if the assumptions are violated. Our essentials for reaching morphogenetic stability are: (1) A network structure that guarantees the possibility of oscillations, (2) a compensation algorithm that guarantees a smooth morphogenesis, (3) kinetic parameters that guarantee convergence in the synaptic elements' change, and (4) a synaptic modification rule that prohibits Hebb-like as well as anti-Hebb-like synaptic changes. It is concluded that many structural features of the mammalian cerebral cortex are in accordance with the requirements of the model.

Algorithms↗
PubMed1993

Stability of r-microbes: stabilization of plasmid vectors by the partitioning function of broad-host-range plasmid RP4.

The genes for biosynthesis of the biodegradable polymer poly-beta-hydroxybutyric acid (PHB) cloned from Alcaligenes eutrophus H16 were used for synthesis of PHB with recombinant Escherichia coli strains. It was recognized that the PHB-biosynthesis genes cause segregational instability to the plasmids used as vectors. Recombinant PHB-plasmids are rapidly lost from host cells and plasmid-free cells occur at high rates, even under conditions of selection for the plasmids. Cloning the partitioning region of plasmid RP4 onto such plasmids resulted in a high degree of stabilization. These par-stabilized recombinant PHB-plasmids could be maintained quite efficiently in batch cultivation experiments in the absence of any selection pressure.

Alcaligenes↗
PubMed1989

Maxillary stability following downgraft and/or advancement procedures with stabilization using rigid fixation and porous block hydroxyapatite implants.

The stability of results using bone plates for skeletal stabilization and porous block hydroxyapatite implants as a bone graft substitute were evaluated in maxillary downgrafts, maxillary advancements, and modified LeFort III midface advancements. The records of 24 patients with greater than 5 mm of forward or downward movement were evaluated cephalometrically, analyzing the presurgical, immediate postsurgical, and longest follow-up radiographs. The 11 maxillary downgraft, 14 maxillary advancement, and three midface advancement procedures all showed less than 1 mm of relapse. Biopsies of the porous block hydroxyapatite grafts were taken on six patients in this study at 6 to 10 months postsurgery. All showed connective tissue ingrowth and 11.3% to 36.1% bone ingrowth throughout the pores of the implants, and no inflammatory response.

Adolescent↗
PubMed2004

The stability of the cemented tibial component of total knee arthroplasty: posterior cruciate-retaining versus posterior-stabilized design.

Micromotion of the tibial component in 40 knee arthroplasties for gonarthrosis was studied using Roentgen stereophotogrammetric analysis. The stability of this component was assessed for 2 years' postoperatively. In all arthroplasties, an attempt was made to reconstruct the preoperative posterior slope. Posterior cruciate-retaining (CR) and posterior-stabilized (PS) components showed at 2 years a maximum total point motion of 0.6 +/- 0.4 mm and 0.7 +/- 0.5 mm, respectively. Whereas 92.5% of the implants were determined to be stable, 1 of the CR group and 2 of the PS group displayed migration between the first and the second year of at least 0.2 mm. A negative correlation between subsidence of the tibial component at 2 years of follow-up and the difference between preoperative and postoperative tibial slope was found. Consequently, we suggest that restoring the original posterior slope of the tibial plateau must be a goal of tibial component implantation.

Aged↗
PubMed2005

Influence of synthetic parameters on the size, structure, and stability of dodecanethiol-stabilized silver nanoparticles.

Metal nanoparticles (NP) are very attractive because of their size- and shape-dependent properties. A widely used preparation of ligand-stabilized metal NP is the two-phase liquid-liquid method using dodecanethiol (DT) as ligand. This work presents various procedures to synthesize dodecanethiol-capped silver NPs, all of them based on a two-phase liquid-liquid method. Small alterations in the synthetic parameters lead to dramatic modifications in the nanoparticles' average size, size distribution width, stability, and structure, as well as in their ability to self-assemble.

Chemical Phenomena↗
PubMed2006

The stability of mRNA encoding IL-4 is increased in pulmonary tuberculosis, while stability of mRNA encoding the antagonistic splice variant, IL-4delta2, is not.

The prototype Th2 cytokine IL-4, and its competitive antagonist IL-4delta2, may be important determinants of outcome in human tuberculosis (TB). However, there are no data on how gene expression of these cytokines is regulated. To evaluate this the stability of IL-4 and IL-4delta2 mRNA after the addition of actinomycin-D, was evaluated in whole blood from subjects with pulmonary TB and uninfected healthy volunteers. The Th2/Th1 (IL-4/IFN-gamma) mRNA ratio in unstimulated cells in whole blood was significantly greater in TB subjects than in controls (p<0.05). The mRNA half-life of the agonist (IL-4), but not the antagonist (IL-4delta2), was significantly prolonged in subjects with TB compared to healthy volunteers ( approximately 5-fold, p=0.0016), and the IL-4/IL-4delta2 ratio was higher in TB patients compared to controls (p<0.05). The differential stability of the Th2 agonist, IL-4, compared to the antagonist IL-4delta2, represents a hitherto undescribed post-transcriptional regulatory mechanism that may modulate the polarisation of Th1/Th2 responses in human TB.

Adult↗
PubMed1985

Discussion on the state of water in the myofilament lattice and other biological systems, based on the fact that the usual concepts of colloid stability can not explain the stability of the myofilament lattice.

Application of the usual concepts of colloid stability shows that the in vivo spacings between the myofilaments, making up the contractile part of the muscle myofibrils, correspond to energies of 10(-4) to 10(-1) kT. Refinements in the calculations of the electrostatic and Van der Waals-London energies do not significantly modify these values. Therefore, theory does not predict the observed stability of the myofilament lattice. It is shown that the interfilament water very likely plays an active role in the myofilament lattice. More generally, the structure of water in living cells is probably different from that of bulk water.

Actins↗
PubMed2000

Stability and stabilization of potential feed additive enzymes in rumen fluid*

Four commercial preparations of fibrolytic enzymes, from Irpex lacteus, Trichoderma viride, Aspergillus niger, and a mixture designed to be similar to the I. lacteus extract, were incubated in vitro with digesta taken from the rumen of sheep receiving a grass hay/concentrate diet, and the survival of major enzyme activities was measured. Some activities, including the beta-1,4-endoglucanase and xylanase from the extract derived from Aspergillus niger, were stable for at least 6 h in rumen fluid. The same activities in the other extracts also retained substantial activity for several hours. beta-Glucosidase and beta-xylosidase activities were much more labile, most being almost completely destroyed after 1 h, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that most proteins in the extracts were digested extensively after up to 7 h of incubation. Adding bovine serum albumin (0.5 g/l) to the incubation increased the half-life of Trichoderma viride beta-glucosidase activity from less than 0.5 h to 3 h. Proteins extracted from plant materials, particularly the soybean 7S globulin fraction, also conferred protection from proteolytic breakdown, but none was as effective as bovine serum albumin. It was concluded that the stability of most fibrolytic enzymes in rumen fluid is not likely to be a limiting factor in the use of enzymes as feed additives for ruminants; but if the enzymes are not stable, means can be found for their stabilization.

Journal Article↗
PubMed2003

Poly(ethylene glycol) as stabilizer and emulsifying agent: a novel stabilization approach preventing aggregation and inactivation of proteins upon encapsulation in bioerodible polyester microspheres.

Protein aggregation and inactivation are major problems associated with the encapsulation of pharmaceutical proteins in biodegradable microspheres. The objectives of this study were to identify the causes of aggregation and inactivation of two model enzymes upon solid-in-oil-in-water (s/o/w) encapsulation in poly(lactic-co-glycolic) acid (PLGA) microspheres in order to rationally develop approaches assuring their stability. S/o/w encapsulation of gamma-chymotrypsin in PLGA microspheres caused aggregation of ca. 30% and halved its specific activity. Co-lyophilization with poly(ethylene glycol) (PEG) substantially reduced the loss in enzyme activity but 8% of the protein still aggregated during encapsulation. Model studies performed under conditions relevant to the encapsulation procedure allowed pinpointing the cause of gamma-chymotrypsin instability, which was mainly the formation of the oil-in-water emulsion. To prevent aggregation in this encapsulation step, the most commonly used emulsifying agent polyvinyl alcohol (PVA) was replaced by PEG because it is known to reduce protein aggregation at interfaces. The use of PEG as the emulsifying agent in the aqueous and organic phase prevented gamma-chymotrypsin inactivation and aggregation during encapsulation. The stabilization approach also worked for the model protein horseradish peroxidase and thus is of a general nature.

Chymotrypsin↗
PubMed2001

Stability-indicating HPLC assay and solution stability of a new diaziridinyl benzoquinone.

RH1, 3-methyl-6-hydroxymethyl-2,5-diaziridinyl-1,4-benzoquinone, is a NQO1 (NAD(P)H quinone oxidoreductase) directed anti-tumor agent. It is designed as a water soluble analog of MeDZQ (3,6-dimethyl-2,5-diaziridinyl-1,4-benzoquinone) and is a drug candidate for clinical evaluation. A HPLC assay has been developed for its analysis. The assay is sensitive (ldl<0.2 ng), precise (rsd<1%), linear (r(2)=0.9997), accurate (error<0.6%), and stability-indicating. Using the developed assay, aqueous stability of RH1 has been evaluated. Both aziridine rings in MeDZQ are known to be easily hydrolyzable in aqueous solutions, however, hydrolysis of the second aziridine ring in RH1 appears inhibited.

Aziridines↗
PubMed1998

Similarities in the biodistribution of iodine-labeled anti-Tac single-chain disulfide-stabilized Fv fragment and anti-Tac disulfide-stabilized Fv fragment.

We evaluated the biodistribution and pharmacokinetics of two different iodine-labeled Fv fragments of anti-Tac monoclonal antibody (MAb) in normal and tumor-bearing nude mice. One was a disulfide-stabilized Fv fragment (dsFv), and the other was a single-chain disulfide-stabilized Fv fragment (scdsFv). The scdsFv is a newly developed type of Fv fragment superior to the dsFv in which the VH and VL are linked by covalent bonds through a spacer arm and by an internal disulfide bond. These modifications increase the yield of scdsFv. Both reagents recognize the alpha subunit of the interleukin-2 receptor (IL-2Ralpha). The biodistribution of the Fv fragments was evaluated in normal mice co-injected with 50 mg of L-lysine and in a no-lysine control group. Biodistribution was also evaluated in nude mice bearing subcutaneous tumor xenografts derived from IL-2Ralpha-positive ATAC4 cells and receptor-negative A431 cells. These mice were co-injected with 125I-labeled anti-Tac scdsFv (6 microCi/0.7 microg) and 131I-labeled anti-Tac dsFv (2 microCi/0.7 microg) or with 131I-labeled anti-Tac scdsFv (6 microCi/0.7 microg) and 125I-labeled anti-Tac dsFv (4 microCi/0.7 microg). The biodistribution of 125I-labeled anti-Tac scdsFv and 131I-labeled anti-Tac dsFv was very similar in all organs and the tumors. The renal uptake of both reagents was blocked effectively (<93%) and similarly by lysine. The scdsFv cleared slightly faster from the circulation than did the dsFv because there were more aggregates of dsFv than of scdsFv (3% vs. 1%, respectively). The scdsFv-to-dsFv ratio ranged from 0.79 to 1.20 in all organs at all time points we examined. In conclusion, the first biodistribution study of an scdsFv molecule shows that the scdsFv had a biodistribution very similar to that of the dsFv and seems to be a good alternative to the dsFv because of its higher production yield.

Animals↗
PubMed1997

Decreased Stability of Transforming Growth Factor beta Type II Receptor mRNA in RER+ Human Colon Carcinoma Cells

Transforming growth factor beta (TGF-beta) is a potent inhibitor of cell growth and tumor progression. Previous work has shown that loss of functional TGF-beta type II receptor (RII) due to a frameshift mutation in the 5' half of the RII gene leads to TGF-beta resistance in a highly progressed, RER+ human colon carcinoma cell line designated HCT116. Expression of this mutated RII gene was highly repressed in RER+ cell lines such as HCT116 and RKO, as analyzed by RNase protection assays. Nuclear run-on and RII promoter-reporter (CAT) assays showed that the transcriptional levels of the RII gene in these RER+ cells were not reduced, compared to RII-expressing cells. However, the half-lives of the RII mRNA, as analyzed by RNase protection assays following actinomycin D treatment, were significantly decreased. This suggested that the decreased expression of the RII gene mutant was due to decreased mRNA stability. Furthermore, RII mRNA from HCT116 transfected with wild-type RII had a longer half-life than the endogenous mutated RII mRNA. A dominant negative RII mutant, which encodes a similarly truncated RII protein as HCT116 but lacks the extensive 3' untranslated region of RII mRNA, gave the same half-life as endogenous wild-type RII mRNA. We conclude that the frameshift mutation which results in a premature stop codon in the 5' half of the mRNA transcript accounts for the reduced RII mRNA levels in RER+ cells.

Journal Article↗