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At least 163 records · Page 9Linked to original sources
PubMed1989

Physicochemical and biological properties of poly(ethylene glycol)-coupled immunoglobulin G. Part II. Effect of molecular weight of poly(ethylene glycol).

In order to obtain a stable human immunoglobulin G (IgG) preparation for clinical use, the chemical coupling of different molecular weights of poly(ethylene glycol)s (PEGs) to IgG molecules was achieved. The abilities of PEG-coupled IgGs (PEG-IgG hybrids) to aggregate were examined when they were subjected to such physicochemical treatments as interfacial exposure, heating, lyophilization, and acid treatment. It was found that the higher the molecular weight of PEG coupled, the more stable was the PEG-IgG hybrid obtained concerning interfacial exposure and heating. The hybrid was stable against lyophilization and acid treatment and its stability was independent of the PEG molecular weight. The decrease in antigen binding ability was suppressed as much as possible by the use of a small amount of PEG of higher molecular weight. The PEG-IgG hybrids were further assessed as a stabilizer for IgG. A limited degree of PEG coupling was required for the hybrids to achieve the most efficient stabilization of IgG; the optimal PEG contents of the hybrid were greater than 20 wt% (interfacial exposure), about 5 wt% (heating), 20 wt% (lyophilization), and 10 wt% (acid treatment) for PEG 5600. It was also confirmed that the PEG-IgG hybrid was superior to PEG and human serum albumin as a stabilizer.

Antigen-Antibody Reactions↗
PubMed1993

Effects of oleic acid/propylene glycol on rat abdominal stratum corneum: lipid extraction and appearance of propylene glycol in the dermis measured by Fourier transform infrared/attenuated total reflectance (FT-IR/ATR) spectroscopy.

Fourie transform infrared/attenuated total reflection analysis demonstrated that the absorbance intensity of C = O stretching bands, which reflect the amounts of lipids in the stratum corneum, decreased with an increase in the duration of skin treatment with 0.15 M oleic acid/propylene glycol (PG) system, suggesting that the oleic acid/PG system induced the lipid extraction, which was followed by a reorganization of the stratum corneum structures. The spectral peaks which originated from the PG molecule were detected in dermal tissues after 30 min of treatment of the stratum corneum with the same system. This observation suggested that the reorganization of the lipid domains due to the lipid extraction by the oleic acid/PG system helped the PG molecules enter the dermal tissues. It was also suggested that an effective volume within the stratum corneum for solutes and/or solvents which could penetrate through the inter-, and/or intracellular routes could be altered in conjunction with the structural changes of the lipids.

Animals↗
PubMed1999

Direct comparison of liposomal doxorubicin with or without polyethylene glycol coating in C-26 tumor-bearing mice: is surface coating with polyethylene glycol beneficial?

Sterically stabilized liposome is characterized by a surface coating of polyethylene glycol (PEG) or other polymers that can reduce opsonization of the liposome by plasma proteins. It has a higher plasma area under the concentration-time curve (AUC), which is believed to correlate with better therapeutic efficacy. However, the presence of large molecules on the liposomal surface may reduce the interactions of liposomes with cells and hinder entry of liposomes into the tumor tissue. Using a stable liposomal system composed of distearoyl phosphatidylcholine/cholesterol, we examined the effect of PEG (Mr 2000) on the pharmacokinetics and on the efficacy of liposomal doxorubicin with C-26 syngeneic tumor model in BALB/c mice. The plasma AUC of liposomal doxorubicin with 6 mol-% PEG-modified distearoyl phosphatidylethanolamine (PEG-DSPE) was approximately twice that of liposomal doxorubicin without PEG at various dosages, regardless of whether the mice were tumor-bearing. Paradoxically, the group of mice treated with liposomal doxorubicin without PEG had higher tumor doxorubicin concentrations. The 72-h tumor AUC was 1.44 times that of liposomal doxorubicin with 6% PEG-DSPE. The tumor-accumulation efficiency (AUC(Tumor)/AUC(Plasma)) of liposomal doxorubicin without PEG was 0.87, and this was more than twice that of the liposomal doxorubicin with 6% PEG-DSPE (0.31). At a dose of 10 mg/kg, although both liposomal groups were better than the free drug group in terms of clinically relevant parameters, including toxicity, tumor shrinkage, and survival, there was no difference between the two liposomal drug groups. In this stable liposome system, surface coating with PEG offered no benefit for liposomal doxorubicin in the C-26 tumor model. To enhance the therapeutic index of liposomal doxorubicin, simply increasing plasma AUC by surface coating with PEG may not be satisfactory.

Animals↗
PubMed2005

An attempt to clarify the influence of glycerol, propylene glycol, isopropyl myristate and a combination of propylene glycol and isopropyl myristate on human stratum corneum.

The present study is a comparison of the influences of glycerol, propylene glycol (PG), isopropyl myristate (IPM) and a combination of PG and IPM (1/1; w/w) on human stratum corneum (SC) by means of differential scanning calorimetry (DSC) and wide and small angle X-ray-diffraction (WAXD and SAXD). The effects of glycerol and PG on SC structure can be attributed to their functional groups. In DSC transition temperatures of lipid fractions are decreased whereas SAXD long distances of lamellar phases reveal an additional interference due to an integration into hydrophilic regions of hexagonally packed lipids (PG) or orthorhombically packed lipids (glycerol). The increased repeat distance is attributed to the polar character of both molecules. However, with IPM the long distance remains unaffected. IPM is integrated into the lipophilic regions of SC lipid matrix as concluded from an increase of WAXD reflections of orthorhombical lipids and a decrease of WAXD reflections of hexagonal lipids. The combination of PG/IPM affects SC microstructure in a specific manner. DSC shows a decrease in transition temperatures of the lipid fractions, although not as much as expected from the single substances. Additionally, the combination of IPM/PG affects the short distances of orthorhombically and hexagonally packed lipids in WAXD measurements similar as PG alone, whereas the long distance seems to remain unaffected as in the case of IPM pretreatment. Adjuvants with penetration enhancing potential reveal different effects on SC lipid microstructure, which have to be kept in mind in terms of formulating systems for transdermal administration.

Calorimetry, Differential Scanning↗
PubMed2002

Global genome removal of thymine glycol in Escherichia coli requires endonuclease III but the persistence of processed repair intermediates rather than thymine glycol correlates with cellular sensitivity to high doses of hydrogen peroxide.

Using a monoclonal antibody that specifically recognizes thymine glycol (Tg) in DNA, we measured the kinetics of the removal of Tg from the genomes of wild-type and repair gene mutant strains of Escherichia coli treated with hydrogen peroxide. Tg is rapidly and efficiently removed from the total genomes of repair-proficient cells in vivo and the removal of Tg is completely dependent on the nth gene that encodes the endonuclease III glycosylase. Hence, it appears that little redundancy in the repair of Tg occurs in vivo, at least under the conditions used here. Moreover, previous studies have found that nth mutants are not sensitive to killing by hydrogen peroxide but xth mutant strains (deficient in the major AP endonuclease, exonuclease III) are sensitive. We find that cell death correlates with the persistence of single-strand breaks rather than the persistence of Tg. We attempted to measure transcription-coupled removal of Tg in the lactose operon using the Tg-specific monoclonal antibody in an immunoprecipitation approach but were not successful in achieving reproducible results. Furthermore, the analysis of transcription-coupled repair in the lactose operon is complicated by potent inhibition of beta-galactosidase expression by hydrogen peroxide.

Cell Death↗
PubMed1975

Function of the classical and alternate pathways of human complement in serum treated with ethylene glycol tetraacetic acid and MgCl2-ethylene glycol tetraacetic acid.

An immunochemical and functional analysis of the classical and alternate complement pathways in human serum was performed in the presence of 10 mM ethylene glycol tetraacetic acid (EGTA) and MgCl(2)-EGTA (MgEGTA), chelating agents which have been recently utilized as a means of distinguishing between these two complement pathways. Total hemolytic activity, integrity of the C1 complex, hemolytic activity of C2, conversion of factor B (C3 proactivator), and complement-dependent bactericidal activity were studied. The effect of these chelators on activation of complement pathways by Escherichia coli, by sensitized erythrocytes as a prototype of activators of the classical pathway, and by zymosan as a prototype of alternate (properdin) pathway activators was studied. Human serum containing 10 mM EGTA, which provides almost no ionized calcium and considerably less ionized magnesium than unchelated serum, allowed consumption of complement via the alternate (properdin) pathway, but blocked the classical pathway as judged by disintegration of the C1 complex and lack of utilization of C2. However, activity of the alternate complement pathway in EGTA serum, as judged by conversion of factor B and bactericidal activity against gram-negative bacteria, was distinctly suboptimal. Addition of magnesium ion in a concentration equimolar to EGTA (MgEGTA serum), while still providing conditions in which the C1 complex dissociated, significantly enhanced alternate complement pathway-mediated bactericidal activity. However, in MgEGTA serum considerable fluid-phase activation of the alternate pathway, as indicated by decrease in 50% hemolytic complement (CH(5 0)) titers and conversion of factor B to its active form in the absence of any activating challenge, was observed. Moreover, some fluid-phase consumption of C2 was observed in MgEGTA serum, even though, as mentioned, the C1 complex was shown to be dissociated under these conditions. MgEGTA-related activation of C2 and of the alternate (properdin) pathway of complement was significantly enhanced by the presence of zymosan and E. coli. These results indicate that use of the chelating agents EGTA and MgEGTA to differentiate between classical and alternate pathway activation of human complement is more complex than has hitherto been suggested. In EGTA serum, spontaneous activation of either pathway does not occur but bactericidal activity, as a measure of biologic function of complement, is suboptimal. In MgEGTA serum, bactericidal activity is fully expressed, but there is considerable instability, in terms of fluid-phase activation, in Mg(2+)-dependent components of both pathways. Thus, caution is indicated in the use and interpretation of the effects of these chelating agents on biologic functions mediated by either pathway of human complement.

Blood Bactericidal Activity↗