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1.
This study was aimed at enhancing the physical stability of the drug clotrimazole (CT) and the polymer contained within hot-melt
extrusion (HME) films using polymer blends of hydroxypropyl cellulose (HPC) and poly(ethylene oxide) (PEO). The HME films
were investigated for solid-state characteristics, moisture sorption, bioadhesivity, mechanical properties, glass transition
temperature, release characteristics, and physical and chemical stability of the drug and the polymer within the HME films.
The solid-state characterization of the drug and the polymer was performed using differential scanning calorimetry, x-ray
diffractometry, and dynamic mechanical analysis. A texture analyzer was used to study the bioadhesive and mechanical properties
of the HME films. The physical and chemical stability of the films, stored at 25°C/60% relative humidity or in a desiccator,
was studied for up to 12 months. CT was found to be in solid solution within all of the formulations extruded. The physical
stability of the drug and PEO in the HME films increased with increasing HPC concentration, but the bioadhesivity and flexibility
of the PEO films decreased with increasing HPC concentration. Films containing HPC: PEO∶CT in the ratio of 55∶35∶10 demonstrated
optimum physical-mechanical, bioadhesive, and release properties. In conclusion, polymer blends of HPC and PEO were used successfully
to tailor the drug release, mechanical and bio-adhesive properties, and stability of the HME films.
Published: June 29, 2007 相似文献
2.
MAPkinase signalling is essential for cell growth, differentiation and cell physiology. G proteins and tyrosine kinase receptors each modulate MAPkinase signalling through distinct pathways. We report here that RGS14 is an integrator of G protein and MAPKinase signalling pathways. RGS14 contains a GPR/GoLoco (GL) domain that forms a stable complex with inactive Giα1/3–GDP, and a tandem (R1, R2) Ras binding domain (RBD). We find that RGS14 binds and regulates the subcellular localization and activities of H-Ras and Raf kinases in cells. Activated H-Ras binds RGS14 at the R1 RBD to form a stable complex at cell membranes. RGS14 also co-localizes with and forms a complex with Raf kinases in cells. The regulatory region of Raf-1 binds the RBD region of RGS14, and H-Ras and Raf each facilitate one another's binding to RGS14. RGS14 selectively inhibits PDGF-, but not EGF- or serum-stimulated Erk phosphorylation. This inhibition is dependent on H-Ras binding to RGS14 and is reversed by co-expression of Giα1, which binds and recruits RGS14 to the plasma membrane. Giα1 binding to RGS14 inhibits Raf binding, indicating that Giα1 and Raf binding to RGS14 are mutually exclusive. Taken together, these findings indicate that RGS14 is a newly appreciated integrator of G protein and Ras/Raf signalling pathways. 相似文献
3.
Nicole E. Brown Devrishi Goswami Mary Rose Branch Suneela Ramineni Eric A. Ortlund Patrick R. Griffin John R. Hepler 《The Journal of biological chemistry》2015,290(14):9037-9049
RGS14 contains distinct binding sites for both active (GTP-bound) and inactive (GDP-bound) forms of Gα subunits. The N-terminal regulator of G protein signaling (RGS) domain binds active Gαi/o-GTP, whereas the C-terminal G protein regulatory (GPR) motif binds inactive Gαi1/3-GDP. The molecular basis for how RGS14 binds different activation states of Gα proteins to integrate G protein signaling is unknown. Here we explored the intramolecular communication between the GPR motif and the RGS domain upon G protein binding and examined whether RGS14 can functionally interact with two distinct forms of Gα subunits simultaneously. Using complementary cellular and biochemical approaches, we demonstrate that RGS14 forms a stable complex with inactive Gαi1-GDP at the plasma membrane and that free cytosolic RGS14 is recruited to the plasma membrane by activated Gαo-AlF4−. Bioluminescence resonance energy transfer studies showed that RGS14 adopts different conformations in live cells when bound to Gα in different activation states. Hydrogen/deuterium exchange mass spectrometry revealed that RGS14 is a very dynamic protein that undergoes allosteric conformational changes when inactive Gαi1-GDP binds the GPR motif. Pure RGS14 forms a ternary complex with Gαo-AlF4− and an AlF4−-insensitive mutant (G42R) of Gαi1-GDP, as observed by size exclusion chromatography and differential hydrogen/deuterium exchange. Finally, a preformed RGS14·Gαi1-GDP complex exhibits full capacity to stimulate the GTPase activity of Gαo-GTP, demonstrating that RGS14 can functionally engage two distinct forms of Gα subunits simultaneously. Based on these findings, we propose a working model for how RGS14 integrates multiple G protein signals in host CA2 hippocampal neurons to modulate synaptic plasticity. 相似文献
4.
5.
Pseudomonas mendocina P2d grew in sodium benzoate at as high as 1% concentration and formed a quinonoid compound, identified as ortho-benzoquinone, that rendered the medium orange to wine-red in colour. The quinone was not metabilised further by the organism. Sodium benzoate was converted to catechol, which was a central metabolite forming ortho-benzoquinone and 2- hydroxymuconic semialdehyde (2-HMS) via. meta ring cleavage pathway. 相似文献
6.
Dhaneshwar S Tewari K Joshi S Godbole D Ghosh P 《Chemistry and physics of lipids》2011,164(4):307-313
Prodrug approach using diglyceride as a promoiety is a promising strategy to improve bioavailability of poorly absorbed drugs and the same was explored in the present work to improve oral bioavailability of norfloxacin; a second generation fluoroquinolone antibacterial. The prodrug was synthesized by standard procedures using dipalmitine as a carrier and the structure was confirmed by spectral analysis. Higher Log P indicated improved lipophilicity. The ester linkage between norfloxacin and dipalmitine would be susceptible to hydrolysis by lipases to release the parent drug and carrier in the body. In vivo kinetic studies in rats indicated 53% release of norfloxacin in plasma at the end of 8 h. The prodrug exhibited improved pharmacological profile than the parent compound at equimolar dose that indirectly indicated improved bioavailability. 相似文献
7.
Manickaraj AshokKumar Navaneethan Gnana Veera Subhashini Ramineni SaiBabu Arabandi Ramesh Kotturathu Mammen Cherian Cyril Emmanuel 《Molecular biology reports》2010,37(1):521-527
Apolipoprotein C3 and apolipoprotien A5 are proteins coded from the APOA1/C3/A4/A5 gene cluster. Sst I polymorphism on apolipoprotein
C3 and −1131C polymorphism of apolipoprotien A5 are key variants involved in triglyceride metabolism and cause a significant
cardio-metabolic risk. Here, we have evaluated these two variants for their roles in coronary artery disease in patients of
the Indian population. The apolipoprotein gene cluster variants were analysed in 416 angiographically determined coronary
artery disease patients and matched 416 controls using polymerase chain reaction—restriction fragment length polymorphism.
The characteristics of the study subjects were analyzed statistically for their association with the polymorphisms. The alleles
were combined as haplotypes and their combined risks were evaluated. The minor allele genotypes of both apolipoprotein C3
(S2) and apolipoprotien A5 (C) had a significant risk for coronary artery disease. The S2 allele genotyped patients had a
significantly increased triglyceride level (P < 0.001) and increased triglycerides were observed among both patient and control CC genotype carriers. We identified the
haplotype S2/C with a significant increased risk (P < 0.001) to coronary artery disease with increased levels of circulating triglycerides compared to other haplotypes in patients.
We conclude that the variants on apolipoprotein C3 and apolipoprotien A5 modulate serum triglyceride levels and increase the
risk of coronary artery disease. 相似文献
8.
RGS14 is a multifunctional protein that contains an RGS domain, which binds active Gi/o alpha-GTP, a GoLoco/GPR domain, which binds inactive Gi alpha-GDP, and a tandem Rap1/2 binding domain (RBD). Studies were initiated to determine the roles of these domains and their interactions with Gi alpha on RGS14 subcellular localization. We report that RGS14 dynamic subcellular localization in HeLa cells depends on distinct domains and selective interactions with preferred Gi alpha isoforms. RGS14 shuttles rapidly between the nucleus and cytoplasm, and associates with centrosomes during interphase and mitosis. RGS14 localization to the nucleus depends on the RGS and RBD domains, its translocation out of the nucleus depends on the GoLoco/GPR domain, and its localization to centrosomes depends on the RBD domain. Gi alpha subunits (Gi alpha1, 2 and 3) localize predominantly at the plasma membrane. RGS14 binds directly to inactive and active forms of Gi alpha1 and Gi alpha3, but not Gi alpha2, both as a purified protein and when recovered from cells. RGS14 localizes predominantly at the plasma membrane in cells with inactive Gi alpha1 and Gi alpha3, but not Gi alpha2, whereas less RGS14 associates with active Gi alpha1/3 at the plasma membrane. RGS14 binding to inactive, but not active Gi alpha1/3 also prevents association with centrosomes or nuclear localization. Removal or functional inactivation of the GoLoco/GPR domain causes RGS14 to accumulate at centrosomes and in the nucleus, but renders it insensitive to recruitment to the plasma membrane by Gi alpha1/3. These findings highlight the importance of the GoLoco/GPR domain and its interactions with Gi alpha1/3 in determining RGS14 subcellular localization and linked functions. 相似文献
9.
Selective inhibition of alpha1A-adrenergic receptor signaling by RGS2 association with the receptor third intracellular loop 总被引:2,自引:0,他引:2
Hague C Bernstein LS Ramineni S Chen Z Minneman KP Hepler JR 《The Journal of biological chemistry》2005,280(29):27289-27295
Regulators of G-protein signaling (RGS) proteins act directly on Galpha subunits to increase the rate of GTP hydrolysis and to terminate signaling. However, the mechanisms involved in determining their specificities of action in cells remain unclear. Recent evidence has raised the possibility that RGS proteins may interact directly with G-protein-coupled receptors to modulate their activity. By using biochemical, fluorescent imaging, and functional approaches, we found that RGS2 binds directly and selectively to the third intracellular loop of the alpha1A-adrenergic receptor (AR) in vitro, and is recruited by the unstimulated alpha1A-AR to the plasma membrane in cells to inhibit receptor and Gq/11 signaling. This interaction was specific, because RGS2 did not interact with the highly homologous alpha1B- or alpha1D-ARs, and the closely related RGS16 did not interact with any alpha1-ARs. The N terminus of RGS2 was required for association with alpha1A-ARs and inhibition of signaling, and amino acids Lys219, Ser220, and Arg238 within the alpha1A-AR i3 loop were found to be essential for this interaction. These findings demonstrate that certain RGS proteins can directly interact with preferred G-protein-coupled receptors to modulate their signaling with a high degree of specificity. 相似文献
10.
The bifunctional protein RGS14 is both a GTPase activating protein (GAP) for Gialpha and Goalphaand a guanine nucleotide dissociation inhibitor (GDI) for Gialpha. This GDI activity is isolated to a region of the protein distinct from the RGS domain that contains an additional G protein-binding domain (RBD/GL). Here, we report that RGS14 missing its RGS domain (R14-RBD/GL) binds directly to Go and Gi to modulate nucleotide binding and hydrolysis by mechanisms distinct from its defined GDI activity. In brain pull-down assays, full-length RGS14 and R14-RBD/GL (but not the isolated RGS domain of RGS14) bind Goalpha-GDP, Gialpha-GDP, and also Gbetagamma. When reconstituted with M2 muscarinic receptors (M2) plus either Gi or Go, RGS4 (which has no RBD/GL domain) and full-length RGS14 each markedly stimulates the steady-state GTPase activities of both G proteins, whereas R14-RBD/GL has little or no effect. R14-RBD/GL potentiates RGS4 GAP activity in membrane-based assays by increasing the apparent affinity of RGS4 for Gialpha and Goalpha, suggesting a cooperative interaction between the RBD/GL domain, RGS4, and Galpha. This activity of R14-RBD/GL on RGS4 is not apparent in single-turnover solution GAP assays with purified Gialpha or Goalpha, suggesting that membranes and/or receptors are required for this activity. When these findings are taken together, they indicate that regions of RGS14 outside of the RGS domain can bind inactive forms of Go and Gi to confer previously unappreciated activities that influence Galphanucleotide binding and/or hydrolysis by mechanisms distinct from its RGS domain and established GDI activity. 相似文献